it works great. the biggest thing is doing your prep and actual application correctly. if you don't it can look like crap. as with painting anything though if you don't take your time and prep good it WILL look like crap. you don't want any runs in it. make sure you clear it also.
they are held on with double sided tape. they also have aligning holes. to get them off you could try to cut through the foam with some dental floss or something similar. just don't go prying on them and damage your paint
sant the part your painting first. wetsand with 800G then 1000G. tack, tack tack it. then spray in thin coats to get the coverage, and darknes you want. thin coat, let dry, thin coat let dry... when your at the darkness you want, wetsand with 1000G again to get it smooth then clear. again thin coats. I do three or four. let cure completly. as in dry for a couple days. wet sand again with 1000G, then 1200G then 1500G and hit with polish. should come out looking like glass.