First go here and say hello please, if you have not done so already.
Have a look over these and welcome.
Nothing really special about evoking him, just having his sigil, his name and some kind of manifestation base, incense, a black mirror/bowl of water, darkness etc.
Best time? At night.
Best offer that he might like? Dra’talon cares for nothing accept the suffering and death he brings, so a promise from you to summon him again to end someone else is the only thing he really wants.
How many candles? Enough to see the sigil with.
What color? Black is the default color for all baneful workings.
My experiences with him, if i’m indoors he always shows up behind me then moves to the southwest corner, if outside same but he’ll move to the darkest area available, i’ve also noticed a rapid decrease in temperature during the ritual that can linger for about an hour after it’s done, it’s also probably best to keep all communication with his as short and to the point as you can, remember he’s nobody’s friend, he’s the very definition of stone-cold killer so always keep that in mind when working with him.
So call him up, tell him who you want dead then dismiss him, make a note of it, then forget you ever did the evocation and let him work, easy peasy lemon squeezy.
And last remember Dra’talon works very slowly so don’t expect your enemy to die right away, death is an afterthought and a blessing compared to the agony he well make them go through.