this is the correct translation:
Mi sarebbe piaciuto avere più tempo per dipingere le modelle".
I've translated literally "to paint the models" into "per dipingere le modelle", i don't think this is what you meant. It sounds weid !
If you translate like that , it sounds like you would have like to paint the body of a female fashion model.
I suppose that you meant you would have liked to have more time for fashion design (for painting clothes on a sheet). In this case, the correct tranlsation should be like that:
"Mi sarebbe piaciuto avere più tempo per disegnare i modelli".
"disegnare" : Is the general verb = write down something on a sheet.
"dipingere" : Is used when you're representing something on paper by a brush. A painter "dipinge" whilst an engineer "disegna".
I hope it has been helpful.