Exactly. Except, those that does that don't train ALL their players, only their fast trainers. The rest are capable but old players bought on the market to fill out the missing pieces. Sell by the end of the season, lower your quality and buy new ones at the start of the next season. Make sure you have 10-12 3* players aged between 21-25 to ensure that your average quality will stay low for years to come in order to get favorable draws.
Personally, I add 2-3 fast trainers every year. I keep my fast trainers and get rid of the rest that are high quality. This season I have 6 fast trainers. The other 5 positions are occupied by older but competent players. I don't invest rest packs in them, only in my fast trainers.