Going to start a new save tonight and give it a go, do i really just leave all training and match prep to assistant?
NO!
Always take charge of training and match prep. personally. Adjust your match prep according to the next opponent and last match. If you miss a lot of chances from set pieces then focus on that. If your next opponents scores a lot of goals and you're playing away then strengthen your defense, etc.
For training I use this setup:
FBs: individual role->fullback. PPMs: Run forward when possible, stay on feet when tackling.
CDs: individual role->central defender. PPM: Mark opponent tightly, stay on feet when tackling, play simple passes.
MCL: individual role->Ball winning midfielder. PPM: Mark opponent tightly, stay on feet when tackling.
MCR: individual role->Deep laying playmaker. PPM: Try killer ball often, dictates tempo.
ML/MR: individual role->Winger. PPM: Run left/right flank, switch to opposite flank, knock ball past opponent
STL/R: individual role->Poacher. PPM: beat offside trap, one-two passes, run into channels, places shots.
You need to also train your free kick and corner kick takers accordingly.
Taking charge of your training camp also will give you the opportunity to develop your youth players for the future so you don't have to keep buying expensive players.