any time i've painted something of that nature i've done it by tackling each section independently. i'm not entirely clear on what section you're describing, but if you can take it apart and spray it that's the route i'd recommend.
if it doesn't come apart, try and find the area where a tape line will be the least noticeable and mask it there, then on your final you can probably go back and blend the area.
same story as above, and i can't recommend this strongly enough, you need to follow their prep and application directions exactly to get suitable results.
caveat: i'm not a professional paint guy or restorer, i'm just three raccoons in a trench coat and sometimes i play a doctor or lawyer on tv. but i have used SEM products with great success and did stay in a holiday inn express the other night.