before you put on a clear coat ( i paint all my rifles so i know a little about this) paint something plastic, like a bucket, tray, gun case whatever, just a portion of it the same brand and color of you base coats. let dry the same amount of time then hit it with your matte and they actually do make a flat clear coat to see if it is compatible. i have had to strip many a stock by putting a different brand matte on at the end of a beautiful camo job only to have it bubble, or crack or wrinkle right off. krylon camo, not the fusion, is some tough stuff and i have found that it will take just about any type of matte. rule of thumb is brand to brand ie rustoleum to rustoleum, krylon to krylon. and about curing time, you were correct when you said the can says 7 days to let it sit longer. that is the key to a good paint job the curing time. i have seen, including myself, guys rush and just wait 24 hours, see that it is dry put it together and go shoot only to find out it has 'melted', smeared or flaked off. bout the only thing that i have found that will take krylon off of a gun and most plastic parts is brake cleaner. i just stripped one last week and that stuff is amazing, but that is about the only cleaner that will damage that paint. just be careful when cleaning it and touch up as needed.