Being vers is the best. In order for anal to not be so painful, lube your hole and practice with toys like dildos and butt plugs. That will train your inner muscles to get used to the penetration if a tgirls pushes your shit in lol. My first experience bottoming was with a fine, mature, almost bbw tgirl with hella curvy features and she had mad girth. Her anatomically correct equivalent would be compared to that of Holly Hung or Honey Foxx and for me having been a virgin at the time of penetration, that shit hurt like hell. All in all, what I'm getting at is the fact that you're gonna have to experiment on what you like/dislike and what you can handle. As far as the nervousness, that will go away over time or with more chemistry being put into the friend/relationship. A convenience store pill or some marijuana will def help with getting it up.