I understand pinholes very well – UGH! I also have tried many surfaces and types of torches and heat gun – in almost every case they are present at least to some degree. Though I’ve heard some people say using a heat gun creates fewer pin holes, I have not necessarily found this to be true. My best advice is to use a gentle, sweeping motion with whatever heating device you are using (torch, heat gun, etc) and use the heat to quickly catch those little bubbles as they arise to the top. Using this method, I can usually get rid of almost all of them without disturbing or “losing” details. This must be done with a delicate touch.
As for getting rid of razor blade marks, again, just fuse gently and allow the surface to cool just slightly
as you do this so as not to lose any delicate marks or details you wish to keep.