Tips! 1. Study them dudes. But where are them dudes hiding their naked skin from use deviants? 2. Find them dudes hiding place, such as the gyms shower, their private shower, their bed...
3. Observe them without even breathing. And use camouflage. If this still don't work...
Then google naked men. Or torment partner/friends/random person at street.
Oh...Still life nude classes are good too.
BUT to be little more serious now, I think you did a pretty good job. Only thing I see is his chest part. I assume, since he is a half-naked belf and a blood-knight by the looks of the armor, he is supposed to be muscular/toned. The chest area looks too flat for such impression but the coloring and the rest is just bad-ass so take it to you or ignore me. After all it is just my opinion.
Oh right I often forget I might be looking at old art. My bad.
I can see that Umbraden for example looks excellent, and I'm actually in no position to criticize whatsoever since my I'm just an amateur. You're welcome and sorry I love your work, you have a new follower!