That all sounds most excellent. I've never thought of infusing with resins. It's opened up a whole new avenue of exploration for me. Thanks!
I'd have thought the viscosity would not be such an issue, once they'd been diluted with IPA, maybe warmed, before the DMT is added? So long as you're diluting enough, for a large enough batch, I'd have thought the end product wouldn't get too sticky.
As for quantities of solvent, going back to my notes from when I first started extractions, with only the Nexus and Nexians for information, I have 40mL of IPA per gram of spice, written down.
I love how into every aspect of the changa production you're getting. I love a bit of attention to detail, me. I've got some IPA that's sat for 2 months with both caapi leaf and vine. I use that infusion for 70% and use another herb for the second, say peppermint. This can be accompanied with a drop or three of the same herb's essential oil on the lid of the container the changa is curing in, or something else, orange, say, or lavender.
I'd always use some damiana infused IPA, as well as having it in the blend
As for the Brugmansia, that species, and it's energy, is always one to to be approached with respect, but I'd have thought that a flower or two, cut up very fine and dried before being well distributed throughout the blend, would be safe as well as interesting, maybe.
Just to ensure you understand, this is in no way intended to be medical advice 
My latest blend:
caapi leaf 0.5g
gotu kola 0.3g
Calea Zacatechichi 0.2g
IPA: 30ml caapi leaf infused 20ml Damiana infused 20ml Pau D'arco
1.11g DMT 0.13g Harmalas extracted from red vine
I have not tried this yet. It's been curing for a good few weeks now. It's potent. I can feel it. I'm a bit scared, if I'm honest.
Hmmmm. Maybe, today feels like the day...