you will have different answers! people use it every week, every days.. etc..0,5 , 1mm, 2mm...but study says 1.5.
In my case I use 1.5 dermastamp for 1st third of my scalp (part I can easily see in front of a mirror) I press 8 times. and the rest of the scalp(middle scap/crown) I use 1.5 dermaroller 8times in all 4 directions. once every other week. Can't say how effective it is but we know it's useful according to differents studies (wounding). you will get the most of it with wounding+topical. but dermaroller on its own can't hurt if done properly(desinfection, use..) and it only takes 5 min for a session when you get used to it...
View attachment 87027