Cutlers resin...fail.

[Tim Simmons]

Sounds like you are using too high a heat and too quickly and burning the substances before melting into a usable substance. You sould not have any problems.
Use a gentle flame from a small spirit/meths burner or even a big spoon over a candle except a yellow flame will soot up. If you cannot find one work with embers of a fire like any native / jungleman.