The key to the low WE guys are:
1. Starting them as much as possible. Starting all 26 games will give you about 4 points of WE in the 10-20 range. Guys who start with a 1 or 2 will not gain any WE, I am not sure about the 3-9 range. I suspect you should see a 1-3 gain for them.
2. Maximizing the blues, particularly the HIHI's. It's not unusual to get 7-9 points of growth from a guy in the 12-15 WE range (I don't have any data lower than that right now) from a blue rating. I am not afraid to put 30+ minutes into a skill if I think it is important.
3. Having realistic expectations. They aren't going to grow 50+ points a season, they won't max out, they won't hit A+ IQ and most of the time they'll be role players.
4. Don't overspend for them. They are a value because so many people ignore them. IF you can afford to start them, sign them for the $110. If you can't, get them late for cheap.