I work for a body shop and we repair FedEx vans and I have to replace the decals (by myself too, it's loads of fun!). The app
paper does pull up the vinyl and cause bubbles. I've had good luck by soaking the app
paper and peeling it off one section of a letter at a time. For example, in the top left corner I pull a little
paper up then make a small cut in the
paper and pull downward slowly so it rips off a strip of
paper covering the vertical bar of the F, and so on. Just be mindful of which way you're pulling and never pull towards a corner or end of a letter.
Here's another trick to make the large Sprinter side decals easier. Their Sprinters don't have side
windows but they still have a recessed area where
windows would be and some of the decals are larger than that area. That means you have to stick most of the decal in the recessed area and heat up and form the parts that extend out the recess. This is pretty easy in some places, but harder in others. But if you look at a decal that is already on the van, they never heat it and make it form into that body line, they just cut the decal and put a strip of vinyl over the gap. The strip blends in so well that you can't really see it. Where do they get the matching vinyl strip? It's right there on the backing
paper above the decal. I always try to heat mine as a matter of pride, but if I'm in a hurry, that's a heck of a time saver.