Yeah it can be pain. The synair and paste is not the best of the urethane products. In fact I was reasonably dissapointed. Sorry.
Anyway, I have used the following types:
* Synair and black paste
* Conathane UC-30 and black paste
* Smooth-on and so-string black tint.
Now that I'm home, I found that my Conathane I packaged up is still good and it is the most superior is terms of plastic with a smooth slippery feel. It also mixes the paste in ok with a good black.
Smooth-On comes with the best tint, the so-strong tint that comes in a small squirty bottle which is so easy to use.
Then we have yours which is the synair paste and you do indeed have to use quite a bit to get it to be darker than dark grey. Use the method following:
1) Pour out your A in one container and B in the next.
2) Use a LOT of black. Experiement as too much will warp the piece. You'll getthe ratio right after a few goes. Mix with a clean sraw.
3) Pour A in container B and mix with another clean straw.
Way you go. You have 3 minutes...
I have quite a few photos to put up with dud pieces as examples. Must get it all together...