I would refer them back to the painters - why do they expect you to finish off their job??
if they pay for you to remove, then thats fine,
i had a custy who had here house painted between cleans, and the windows were covered ( really badly ) i pointed this out and said she should get the painter back, to which she said i've paid him now.
So we agreed a price for me to remove paint - 2 hrs work.
Darran