im very new to this site (joined yesterday) and new to bdsm but not new to fisting mmmmm i love it
may i suggest( if He will allow) the way i started untill i learned to relax enough automatically
we would start off with foreplay then he would use plenty of lube and have his arm in a way that i could sit on it and slowly lower myself onto him while playing with my own clit strange but it worked as it was at my pace when it got uncomfatable i eased of for a second then went back down worked for me