If the coil is like new, meaning no scuffs or scratches, then like Neil said a while back it might be a good idea to lightly sand the surface before putting the spray on liner on. I didn't do that with any of the three coils I sprayed and they have held up well. About 3 or 4 coats is all you need spaced apart about 2 or 3 hours apart or so. I did it mainly to keep the weight down on my light weight machine as much as possible, but it's also great for not having to clean under coil covers. That gets very important when water hunting.
A friend's Excal 8" coil was splitting due to him using it for 4 or 5 years without a coil cover and scrubbing the sand under the water. That's why I put about 8 or 9 coats on it, to be sure it was sealed good and fill in those gaps. I stuck some Shoe Goo in there but I think it'd be better to not use that since it's likely to peal off. Just spray the bed liner on heavy if there are any splits or gaps in the coil. Last time I checked his coil it looked as good as the day I put it on, but again it was already scuffed up from the sand.
If you water hunt and the coil is new it might be a good idea to do what Neil said and sand the coil a bit so it sticks well. My coils were pretty new but I didn't sand them because nobody ever said you needed to do that. I'm mostly a land hunter and so they've held up well. The 10" coil is for my water hunting and thus far it's holding up fine after about ten hunts, but I'm going to monitor it to see if it flakes or chips off due to me not sanding it. If that happens I'll just scuff up those areas and re-spray it on. The most important thing is to wipe the coil clean of any dust or finger oils. One of those tacky clothes for $2 in the auto body section of a parts store works real well for this. Tape the top of the coil up with blue painter's tape. I noted where the coil cover ended on the side of the coil and made sure the tape was above that in general for good side protection of the coil. The edges will wear out just as fast as the bottom without protection, probably even more so when water hunting because the sand floats up and over the coil.