I taught myself to be able to throat any size dick.
--I lube up the dick first. Lube helps. I use a silicone lube but most any will do.
--My favorite position is lying on my back on the bed with the guy straddling me. He faces my feet. I find this really lets me open up the throat and the dick enters in at a good angle.
--Try to find a guy who really knows how to face fuck and force it in. For me at least, that really helped. LOL. Seriously, this was really sexy to me and helped me get into.
--Do your deep throating on an empty stomach. First thing in the morning was a good time for me.
--Personally, I never practiced with a dildo. It didn't work for me. Though it sounds like it works for some so you might try it.
Enjoy. Keep towels handy in case there is any mess.