>>2292837find gay porn blogs on tumblr or wherever and draw some stuff using the photos as reference. dont trace, but "eyeballing" is okay - though early on its gonna look obvious, so if it were me i wouldnt post the early practice stuff. and be sure to mirror/flip your drawing OFTEN to check for mistakes. this is the best advice i have for anatomy practice, sorry it's not much.
also, when people look at porn of anime and vidya boys, they dont usually expect or even want exact realistic anatomy, so it's okay to exaggerate things a little if it looks better? but using real pictures to reference is super important. and when youre bored just doodle lots of dicks and asses and stuff
oh, one last tip, and this is true for me but maybe not everybody: i cant draw for shit when im horny. if im drawing porn i need to have a clear head.