Yeah. A ton. First, water enema. I know that kinda is a mood killer but all I have to say is try it 4 hours before Go Time, then formulate an opinion. For some reason it’s just easier on the physical process in my experience too. Next lube or a ton of thick spit.
Now for the most critical piece. It’s not you per se. He needs to warm you up. If he is huge, I think you would have mentioned it so I’ll assume he is a bit bigger than average.
A finger, then two, while he fucks your pussy. Then the lube/spit. Then push the head in, with pressure, and when the pop happens, he needs to just hold it there and let you adjust for a good 15 seconds. Then push in further all the way back. Then wait again. Then slowly and eventually work up to full blown fucking.
Also, positions I find to be easier on the girl tend to be her bent over, even standing. Doggy over missionary.
Not sure if the plugs are helping anything too. You’d be better off with something shaped like a cock that he can push in and out repeatedly (like an anal vibe) instead of something just sits there like a plug.
Geez. I just talked about the most detailed inner workings of butt sex for 5 paragraphs.