[Maritime Q-Scout]

Crazy Flamer, that's a complex situation indeed.

What remedy does the neighbour to the left desire?

Paint thinner and alcohol was rejected by them. Not being a roofer, nor a painter, nor any time of handy person, I don't know how reasonable a solution that it (I mean, it may be, I honestly don't know).

Find out what they're looking for. If it's a new roof, I'd say 'no' but perhaps the shingle(s) could be replaced at a reasonable cost (especially if you have a friend that is a roofer). Again, I know nothing about this stuff, but I'd find out what solution THEY want as opposed to making a suggestion yourself.

Once you have that, then work forward.

If a buddy and a case of beer can fix the situation voila.

Ultimately, the painter should be liable. But if it was a friend of a neighbour then, following up is a little more difficult (assuming they aren't insured for painting negligence).

Thinking as I type, a buddy of mine has a painting company here in NS. I can find out how he'd fix this.