it really depends
you can relax outer muscle but inner muscle there's no way you can relax it manually, penetration should happen and it will relax itself,
doing it yourself you can control, you know when to let go, when to pull out or push it in,
other they won't know, most guys just pushes right in, "what that's what they do it in those porn"
thats why they go by fingers, actually its quite different, Hardened soft tissues are still a soft tissues not a bone,
relax, find the right time and atmosphere for both of you and your partner,
if you rush it it will happen,
or like me, anybody can fuck me anytime, I would feel pain but I'm used to it to the point I actually enjoy anything, its a penis, lol