Replying to Help on PROPERLY using clear p-tex?

Got a nasty ding on my AR7s right by the edge from the winter break and I'm a little sketched about using the clear p-tex on my bases...

I've search barred and there was lots of mixed comments and ideas on how to do it, there was also a video on it, but it didn't contain what I was looking for...

I hear that clear p-tex can be harder to apply due to the fact that black stuff can form on the p-tex and discoloration; I don't want any of that!

So NS, any p-texing pros that have experience in using the clear p-tex, can you help me out?