So I asked this pretty much same question to Rasky on here. He basically said we are using the wrong type of tape.
Apparently what we are using are meant for hard to stick to surfaces, so basically you need to get one that doesn't stick to much, but just enough to be able to peel with no residue. Let me see if I can find his post.
As for your second question, polish does not have to eventually in there. Work your product in for a minute or so on the paint, and then cross over the seam and you will have no sling of polish into the cracks