I assume you are talking about vaporizing dmt?
If so, it is not as hit and miss as you might think.
If you want to breakthrough, no questions asked do this:
1) get 60mgs of quality spice
2) get a water bong
3) get some mj, blue lotus, white lotus, parsely (in a pinch) or some other smokeable herb that is not too harsh
4) put a SMALL amount of leaf down in the water bong (leave room temp water in bong)
5) spread out your 60mgs of xtals, keep it away from the edge of the bowl
6) add a small amount of leaf, enough to barely cover the spice
7) try and kill the bowl in 2-3 large hits. The first is the most important, make it as big as possible and hold it as long as possible. Don't leave your lighter on the bowl longer than needed to light a cherry.
If you do this you I would guess your changes of breaking through to be about 95% (unless you are on SSRI's or major tranqs (thorazine, etc)).
This can also be done with a regular bowl, but the smoke will be a bit hotter and harsher.