here is a durablock sander demo. the guys have an english accent, lol, but it does show the method well. the guide coat he is using is a dry carbon product. it is awesome but a bit spendy. don't use the felt marker tip I suggested on already primed surfaces as it tends to sink into the primer and will show through the paint possibly. thaty tip was for the bare metal process and I should have mentioned that, sorry fellas. the dry coat style works great or there is also sprayable guide coats of a different color than the primer so you can see when it sands off.
https://www.youtube.com/watch?v=RUzARNKYYhw
https://www.eastwood.com/ew-guide-co...QaAjLBEALw_wcB