Dermarolling or dermastamping is successful in reducing or improving scars but unfortunately it seems it doesn't do much for pore size. Pores are ducts in the skin and their size is in our genes.
You cannot change that. So far I have not heard success stories from our customers concerning reducing their pores. (They report improvements in scars or pigmentation etc but not in pores).
There are currently no methods that can significantly and permanently reduce pore size. Acid peels in some cases reduce pore size but only temporarily.
Some (not many) customers even wrote me that after laser treatment (intended to reduce pore size), they ended up with larger pores than prior to treatment.
If you have scars, there is a big chance for improvement but if you have "just" pores, the chance is small.
Yes, a dermastamp seems more suitable than a dermaroller in your case. You can use it every day but do not stamp the same scar more than once a month.
No, vit. C should not be applied right after dermarolling with long needles. It is acidic and it would sting.
Apply vit. C two or three times a week for general skin care (vit. C is very important for the skin). Apply it also for four consecutive days prior to dermarolling or dermastamping to achieve maximum skin levels for the day of treatment.
Restart applying 2 days after dermarolling and apply it two or three times a week. Vit. C is sensitive to light so apply it before you go to bed.
A copper peptide mask can be applied right after dermarolling but some customers ended up with temporary red skin, Do a test patch on a small skin area to see how your skin reacts if applied right after dermarolling.