Just practice flipping your bunny on his back regularly so he gets used to being in that position. When bunnies are on their back they kind of go into this weird state where they are in “trance” and relaxed. Sheep do it too 
Anyway when you’ve got him on his back, play with his toes/feet so he gets used to it. If you’re worried about quicking him on accident, just trim off a tiny bit at a time, but cut his nails weekly or biweekly instead of monthly. It’s not a bad idea to keep corn starch aroundjust in case he is quicked and you have to press some on the nail to help it clot. If you do quick him, you’re not a bad person and he will be fine
It’s a small thing like stubbing a toe that bleeds that everyone who trims their own pet’s nails has done at one time or another 
I attached a picture of the trimmers I use on my bun- they are like scissor nail trimmers. They ares small enough for a rabbit and easier to handle for nail trimming than other dog nail clipper styles that I use on my beagles. The only clipper style I would not suggest is the guillotine style where you stick the nail through the hole. It is easy to split nails with that style and is harder to see on both sides of the foot what you’re doing, IMO.
