When you say 'blank lineup', do you mean you just select the guys who can play at the top. Then set tactics and leave the rest?
I have no experience with this at all. Although I am intrigued to give it a go.
I do it in the private league each week. Works ok but less control over minutes. If you only have 1 or 2 trainees I guess you would just name them in their spots and leave the rest clear.