Uh...I'm sorry, but the positions mentioned here are probably the worst positions to slow build. The positions that get the most points in certain attributes per level up are ultimately the worst ones to slow build, and the best ones to cap build.
We'll use Centers, for example.
Players 1 and 2 each roll a 28 STR 14 BLK C.
Player 1 rushes his C to 49 STR by level 2. Then, he trains Blocking until he has enough points to softcap it at level 8. He now accumulates points until level 13, when he decides to join a capped team, all the while training Confidence to try and prevent penalties, and with the intention to get Line General up sooner rather than later. At level 13, Confidence would be around 25, and he would have around 25 points saved up, so he softcaps it.
Player 2 trains STR until it gets too expensive, at which point he begins training blocking until it becomes too expensive, then switching to confidence. When he joins a capped team at level 13, he adds points into STR, BLK, and CON to catch up to Player 1's stats.
By level 13, Player 1's C will have 60 STR along with 54 Blocking and 49 Confidence. He has 0 points to spend.
Now, I'm going to give player 2 some credit here and say that he manages 30 STR, 30 BLK, and 25 CON by just training up to level 13. He now has saved 75 points to add to his C. 30+19 to reach the 2-for-1 point, and then to catch up to Player 1's C's STR, he needs to add another 22 points. That leaves him with 34 points to add to Blocking, so he gets BLK up to 49[15 pts] and then adds another 10 to get it up to 54, leaving him with 9 points to get Confidence up to 34. The difference is insane; the exact same STR and BLK with 15 less Confidence at the exact same level.
If you're going to slow build, do it on a position like QB, HB, WR, FS, SS, CB, etc. that has more than 4 major skills that get points every level up.