Sure you can spot treat with retin A, it makes higher cell turn over. Why fix something that is not broken. People spot treat with TCA peels as well. Make sure you wait a few hrs after the derminator procedure if you decide to use it after, in case it's not sterile (on top of skin, not inside).

Yeah, i was thinking to use retin a twice a week and the rest of the days a home made vitamin c serum.

My only concern about this is, how much do you aply if you only do the scars...

Pea sized amount rub into scars. You know your skin better than me, skip some days if sensitivity