If you want a PG, don't train JR right now like DanielPaton suggested. If you want an SG, I still wouldn't recommend training JR at his young age. Not only would it make his salary increase in a short amount of time, he would have some valuable cap space eaten up. According to the USA Offsite Training Planner, it takes ~2.7 training weeks for JR to pop, and that's on an 18 or 19 YO. Not fun.
I would get his PA to 7-8. The elastic effect will make it pop faster than usual, and PA already trains really fast on every position. Then, I would get his OD to 9, then work on his HA/DR using 1v1 Guards until they are at 9. Then I would work on his JS during weeks where you can't 1-position train him (weeks where he doesn't get 48+ minutes or during 2-game weeks.