The main active alkaloid is usually 5-MeO-DMT, even though there is usually about 4 times as much DMT present. 5-MeO-DMT is 2-10 times as potent as DMT (depending on the individual’s sensitivity to it) and tends to overpower the effect of DMT even when very active doses of DMT are used. 5-MeO-DMT is active at 2-10 mg vaporized, but it needs to be vaporized very quickly.
This plant usually has about 0.4% alkaloids (up to 1.7% is reported) and often 20% of that is 5-MeO-DMT. So we're talking about 0.08% 5-MeO-DMT usually. So to get 4 mg of 5-MeO-DMT, enough for very decent effects, you'd need to smoke about 5 grams of leaves in less than 3 minutes. Or do the technique below.
The best method is to use a very large pipe bowl with a water bong. Add 4 grams of leaves and heat the leaves until they are smoldering, but don’t torch them (don't let the flame touch the leaves). Only smoke half of the bowl each time, and do it very slowly, and then add 2 grams more. The idea is to let the 5-MeO-DMT accumulate on the bottom of the bowl. The slower you smoke it the better. Do this about 4 times, adding more each time. You won’t get much effects from it yet. Now wait 30 minutes for any built up tolerance to pass. The 5-MeO-DMT will have built up at the bottom of the pipe bowl and provide you with a decent trip by smoking all of the remaining material in the bowl as fast as possible. Don't hold the smoke for more than 5 seconds. Exhale through your nose and immediately inhale as much as you can, and repeat. A lot of the 5-MeO-DMT and DMT quickly solidifies in the lungs and nose as you exhale (they are both also active intranasally) and gets absorbed into your blood stream. The idea is to get as much 5-MeO-DMT and DMT in your lungs and nose as quickly as possible.
This is wasteful, but really the only way to get good effects from leaves that SWIM has found.
Another way is to smoke some MAOI plant first (like peganum harmala, caapi, etc.). Smoke until you feel the effects, and then smoke the D. cabrerana. That will boost the potency if the leaves by 2-3 times.