Nice! Sounds like you’re going great, that’s exactly how it works 
You can use the tutorials here to try it out, or you can follow the methods from a book.
Here’s a simple and easy to use evocation ritual that is close to what I do, and I use sigils not enns:
No it’s not rude at all, they rather like it usually, as the physical realm is interesting and fun for them. They would like to be able to manifest in it on demand and walk the Earth, but it takes a lot of energy so we help.
As far as I know, the idea that “evocation is rude” is an opinion taken by followers of the religious current called Demonolatry, who worship “demons”. Enns are from demonolatry. Which is why most entities don’t have enns. Me, I’m allergic to religion and see worship as anti ascension, disempowering and disrespectful to yourself, so I don’t use enns because they feel kind of… eh, tainted? to me. But that’s just me, if they work for you then that’s great. If it ain’t broke don’t fix it.