Some thoughts on vinyl paint masks.
When I transfer vinyl from the backer to a substrate at the signshop, I use a very low tack tape, I just call it paper tape, transfer tape is another name or application tape. While still on the backer, I will often throw it on top of a light table and create a registration mark, just so I have a reference line in which to measure from. A window works just as well, if there isn't a light table around.
Once the vinyl has been located on the wing, and you've measured it at least six times ( I know, right?)..., tape down one edge, creating a "hinge" , fold it over remove the backer and place it gently on the wing..that way if you have to move it you have to...however I find that if i have to move it, then the second placement requires a bit more burnishing as some of the adhesive has been removed, if that makes any sense.
If the transfer tape seems to be holding onto the vinyl mask a bit too aggressively, warm air will soften the adhesive, usually your breath is fine, just get close to the transfer material, peel back an edge and breathe and peel..it should do the trick...if it doesn't another trick is a bit of water on the transfer tape, not a lot, don't drown it..you just want to soften the adhesive on the transfer tape enough to remove it from the mask.
When the mask is in place and and I'm happy with the placement, I just burnish it down on the edge, seems to work for me, but that's just me, you may want to burnish the whole mask down, up to you.
Another thing I do, is cut more than I need, so when I make mistake, which after almost 25 years of doing this kind of thing, I still do, then I have another mask in the line up ready to go..I hate having to re cut vinyl..and it's not like I won't use it again.
If it's a particularly complicated mask, or paint surface, I may do a sample on a spare piece of material going through the same steps of degreasing, priming, painting that I did on the scale model to see if there is any chance of a mask failure..we've all been there, so you know what I mean. it's a bit of extra time but I think it saves a lot of heartburn later on.
These are things that work for me..you may find something in the above that works for you. You may not.