I am both (actually have more experiecne being active) but am glad to answer on behalf of bottoms.
topmen: It's not taking your time. Most guys need to be relaxated and warmed up...it's called foreplay! Massage, making out, rimmming if you like that......in my opinion, the idea of ramming it in hard and fast exists mainly in porn. In real life, most guys need some slow build-up and time to relax.....then the pleasure will be intense, without any pain at the beginning, which is typical....wait til your guy is literally begging for it....that means he is ready for you. Go slow, tease him, make him want you in all the way before you settle in with all your weight....