What I think I lot of new bottoms, or people who are afraid to bottom, don't understand is that it's not the same in real life as it is in porn movies--namely, you don't pull the bottom's pants off and then immediately shove your hard cock up his butt.
The key to good bottoming is lots of prep work. Make it part of the foreplay or the sex itself. Start off by rubbing around the hole. Then slowly insert the tip of one finger. Mentally, the bottom needs to relax the anus and just breathe. Use LOTS of lube! Once that feels comfortable, stick the one finger deeper in. Then eventually work your way up to two fingers or more. Play with a small dildo or other toy. Eventually you will get his hole so relaxed I bet he will be begging for the real thing.
The first few times I tried fingering myself, it hurt like a mother! It slowly got easier. I finally bought a small dildo but psychologically just wasn't ready to stick anything that big up my butt.
Finally, one night, I just decided to do it. I remember I was watching the Matt Summers gangbang scene at the end of "Detention." I lubed up that dildo and just went for it.
Oh my god. Words can't even explain the first time. I thought it was going to come out of my belly button, but I didn't want to stop. I just started bouncing up and down on that thing, eventually taking it harder and deeper. My eyes started rolling back in my head, my legs started quivering, and I thought I was going to faint. When I finally came, I EXPLODED! It was the best orgasm I had ever had in my life up to that point. That did it for me and I haven't looked back.
"A weiner up their butt doesn't actually feel that good"?!?!? Um, it's only the most amazing feeling EVER!