Do you know WHY you get carbon in the ptex?Before you can eliminate the carbon from the PTEX drip, you must understand why it forms.
The very thing which allows the candle to burn is also its greatest problem. WAX. The average PTEX candle is impregnated with wax so it will burn. Pure PTEX will not burn, but will melt nicely if a continuous heat source is maintained.
When you light the PTEX candle, the amount of oxygen determines the heat of the flame. The more oxygen, the brighter the flame, and the more carbon build up will occur. When you hold the candle tip very close to a surface, such as a metal scraper (as has been advised earlier) the amount of oxygen is reduced, causing the flame to burn cleaner, with a small blue flame. While the candle is burning, rotate the candle while rubbing the side of the melting zone on the scraper. This will remove most, if not all of the carbon.
When you drip this candle into the gouge, it does not bond cleanly, because of the wax. And those welds that do hold may gradually wear away, as the wax impregnated PTEX is much softer than pure PTEX.
A trick I learned many years ago is to, after filling the hole, come along with a lighter, and reheat the weld material. While it is in (or near) liquid form, take that same metal scraper and an insulator, like a cork, and press down on the weld with as much pressure as you can develop. Remember to put your hand on the cork, on top of the scraper, or the heat will come right through the scraper and burn you. Hold this for about a minute, and not only will you have a stronger bond, it will also be cleaner/ smoother. This reduces the amount of time it will take to make it uniform with the rest of the base.
So- as you can begin to understand, pure PTEX is much more preferable to the burning candle type. It holds better, is easier to work with, and lasts longer.
Some may think it a splurge item in a tuning kit, but an extrusion gun and some pure PTEX sticks can be had for under $100. If you think that is expensive, look at the repair work you can do on your $1000 skis! And your friends skis... (think many beers or possibly even a little cash...
Given the inconsistent seasons being had around the country this year, I think a PTEX gun would be a very wise investment! And you can get both clear and black PTEX for the gun.