IR heater - These things have so many uses; use it to evenly heat the vinyl as you pre-stretch bumper corners, Post heat large areas, heat up vinyl for removal (wraps, cut vinyl, or window perf), heat up your install bay and or preheat or dry a cold vehicle.
These things are awesome.
Summit Racing is another place you can buy them.
Glass will only break if you concentrate a lot of heat or cold in a small area. Chances are, you would smoke the vinyl before you break the glass, If you keep a torch moving it won't break. An IR heater is defiantly safe because it's a wide slow heat similar to the sun.