He's 20 already, so I wouldn't bother. You can find tons of good players right after the draft. I mean, I got a decent MVP, listed him at 1k starting price.. and he went for miserable 50k.
Your guy is pretty well rounded now though, so you could train him for a while, could be a useful backup in lower leagues.
How about just training each skill until it pops? Use his sublevels to make him look better, maybe you can even sell him that way.
You could go JR,OD,PA,ID,SB,RB then 1v1 until HA and PA pop, finish with IS and JS