I'll third the heat gun. I have an old hair dryer (wish I had a good heat gun), and with patience, it works for me. As far as removing left over glue gunk, I have had best results with WD40 and more heat. I think the WD40 keeps the gunk from resticking to the plastic as you push it around. I then use Dawn dish detergent, then contact cleaner to get the WD40 (and whatever else) off.
The “bubble problem”. I always try to start large graphics in the middle then work to the edge. Any bubbles near the edge I get out by pushing a needle (a thin very long one) in from under the edge of the graphic to the bubble, then work it out, bubble to edge. It takes me forever to put on graphics, but I get good results.
I have read that other people (probably more knowledgeable than me) put Windex or mildly soapy water under the graphic; so that they can move it around then work out any bubbles. I have not tried this yet (have worried I will not do it right, so will not get good sticker adhesion). Maybe someone who does this can comment.