I have been trying to open sastans sigil gazing into it for several days now.
Nothing happens. I ask sastan to talk to me, give me a sign hes there, help me get into the theta gamma sync, help me open his sigil all to no avail.
This theta gama sync thing is a hurdle. How the heck do I do this thing.
This is a catch 22.
You do not always need to get as deep as Theta for magick.
All you need to do is obtain a basic Alpha level trance state, which is very easy to do, as you enter one every time you watch TV or lose yourself in a movie.
The Theta/Gamma sync is only necessary for the physical materialization of spirits through evocation, and only if you wish to see and hear them.
The key to entering a trance state is to relax. The harder you struggle, the less likely you will enter the mind state you want.
Try doing some progressive relaxation before opening a seal. Relaxing your body will relax your mind, and can put you in a light trance on its own. Follow it with a simple, self hypnosis countdown from 20 to 1. As you say each number to yourself, say something like, “20, I sink deeper, 19, still deeper, 18, I relax even deeper…”
When you finish the countdown you will be in a deep Alpha trance, and can open the seal. The more you practice an exercise like this, the easier it becomes and the deeper you will go. I’ve been using something similar for years and can go as deep as Theta easily now.
Does the spirit speak to you when you open its sigil?
No, not always. It depends on your intent.
For example, in EA’s evocation course, you simply open the seal of Sastan with the intention of getting his help and then you practice scrying using whatever method you are working with. There is no need for the spirit to say anything because he already knows what you want him to do since you projected that intention when you opened the seal.
In another exercise to develop clairaudience, you write down 5 questions to ask the spirit, and then open the seal and call to the spirit to answer them. You ask the questions and then write down whatever you hear.
In both examples, the intentions are different, and the spirit responds to each of them in whatever way is appropriate. Opening a spirit seal gives you a line of communication but you still have to call the spirit forth to establish communication. That is why opening the seal is only a preliminary step in evocation.
You’re pushing too hard. The keyword here is to allow the sigil to open. Can you visualize a flower opening into full bloom?
I have been working with spirits for a long time. The trickiest part, aside from interference/noise is to trust what you perceive without projecting. It’s a learning process, and it requires you to take yet another step into the zone of belief that you’ve been conditioned to ignore your whole life.
Keeping a detailed journal helps a lot - write your perceptions, verify them later.
When listening for clairaudience, don’t reach for or grab at the impressions, the voice, because you will push the message away. It’s necessary to practice active reception, and when it starts answering, just listen, don’t leap at it.
Hope this helps.
Take a step back.
If watching the corners of the wall isn’t doing it for you, practice basic mindfulness: consciously relax your body, focus on your breathing, observe your thoughts, then observe the empty nature of your thoughts, sink into that state of non - thought.
Open your eyes at the point when you are relaxed and clear and transfer your focus from your breathing and mind to the sigil in front of you. Try not to blink. Pretty soon it’s going to start flashing, appearing / disappearing. The process begins when you begin to see an aura around the sigil. After the flashing it seems to lift out of the page. Transfer the intent to see spirits into the sigil. It’s at that point, when the sigil is fully charged that you should begin gazing into your skrying medium, whether it be incense, fire, water or blood. If it’s completely dark around you, spirit forms will manifest in the darkness. Eventually, you will come to a point when you can bypass all of the above steps and spirits will appear in the darkness before you as a matter of course, especially in the hypnagogic state between sleeping and waking (which is itself the theta - gamma synch).
Ok here are some suggestions… 
Sit on a chair in your circle and chill,
It’s all about contact+genuine relaxation,
Thinking about just one thing, contact with that entity…;
Nature is an excellent place for energetic discernment, in a place where you can sit, chill and feel undisturbed, or a singular temple space or physical altar,
Refocuss your mind to the spirit by keeping talking to it, you can ground that effect by writing, also for example, .
Focus, keeping that focus through using your thoughts, breathe deeply to stay grounded and to integrate the deeper realised states to stay in touch with the physical realm, you can use candles, inscence, walk around the circle in circles, counter clockwise for a - polarity being and + for a +polarity being,I guess that for spirits as middle beings, you can choose.
It’s all about relaxing while staying conscious and in touch with all levels of reality, going inside varied with consciously grounding it,
Ever the invite the spirit in in the name of the source, to embody it, to allow it in, you can ask it verbally to ground that command…
Conscious relaxation, and focus, …surrender, entering it , becoming it, trust yourself, step by step to go deeper into flowing with or into the feeling of the spirit, to embody that as you have your attention with it, (by calling it’s name)
Make it all about that spirit.
Drawing it’s sigil yourself opens up your very own consciousnes to it. It’s more powerful than using an example though it works.
Let me know how it works
Scrying with tools was always much harder for me than just shifting my mental focus.
If you always use the same incense and, if desired, (unobtrusive) music, it triggers the subconscious to begin to enter the proper mindset as soon as you smell/hear it.