If you JUST finished Accutane, I would go really really slowly with the Tretinoin cream, for your skin may be quite sensitive right now (I've used Accutane 5 times). I would only use Tretinoin on ONE red mark every other day for the first one week to see how your skin reacts to it. If your skin doesn't seem to be irritated by it, you can increase it to once every day for another week. If your skin seems to react positively to the cream, then I would use it on all other red marks, sparingly. The key word is 'sparingly'.
I personally have tried almost all of the Vitamin A cream available on the market: tazorac, differin, Retin A, Renova, Avita, etc....... All of them except Tazorac irritated my skin. However, I used Tazorac following the method mentioned above. With other Vitamin A cream, I applied too much too soon.
If you want to know the detail of my skin regime & how I have finally conquered the battle w/acne, pls read my very recent post, with the topic, "Finally beautiful skin without oral medication".
Good luck & best wishes to you