Most P-tex sticks have basic wax as part of their make up. I find that burning, letting it flame and then drip on to the ski does two things, allows carbon do develop, and lets the P-tex cool before contacting the ski. This and trying to fill larger dings seem to be the cause of cracking. Clear p-tex show more carbon then other colors, twisting the sicks also helps reduce the problem.
Over the years I have adopted a method where I use a small butane torch (cleaner fuel, less carbon) holding it upside down to keep the flame from touching the ski, I then work the p-tex with the flame close, then
try to run it as a welding bead.
This does take a few tries to get good. So find and old ski or maybe you friends.
Now for base welds. Base weld are done when the damage goes into the core of the ski or beyond base thickness. Base welding material has an epoxy core that is activated by the hear of the welder.
If you don't have access to a welder and need a fast repair on a deep dinger. the trick is to put down some cyanoacrylate (super glue) into the hole to insulate the core of the ski, let it dry then you can use p-tex to fill.
Hope this helps.
