How I finally got a smooth mask job on tricky paint

Did something similar last fall on a two-tone F150, big stripe down the sides that the owner wanted to keep and clear over the whole bed sides. I did not double tape the seam like you did and paid for it. One panel bled about a fingertip's width along the stripe and I spent a whole Saturday with 1500 grit and a soft block fixing it. Since then I run a second tape layer over the seam and burnish it down with a felt squeegee before anything gets sprayed.

One thing that helped me besides what you said about paper edges was folding the tape edge back on itself for the last half inch at the end of a run. Gives you a little tab to pull the whole line off clean after curing instead of picking at it with a fingernail. I also learned to peel the tape while the clear is still tacky, not the next day. Waited overnight once and the edge had glued itself down good, pulled up a sliver of fresh clear with it. Now I time it so the last panel is just set by the time I walk the tape off.

And yeah on the time thing, my wife knows if I say masking will take an afternoon, don't plan anything for the weekend.

New here, mostly lurking, but this hits close to home. I only do this stuff on my own old Jeep in the garage, no customers, and I still learned the hard way about rushing tape lines. Did a hood refresh last summer, some pinstriping I wanted to keep, and got impatient with the edge prep. Ended up with a wavy line you can only see at the right angle, bugs me every time I wash it. One thing I'm wondering, do you guys ever score the tape edge lightly with a blade before peeling it on bigger curves, or does that risk cutting into the clear?

Second layer of tape over the seam is the way, that part saved me on a boat hull with a waterline stripe I had to clear around. What made the difference for me was warming the tape with a heat gun on low before pressing it down, sticks way better on the curve and no bleed the whole length. Curious if anyone else does that or if it's just a hull thing.