I've heard using white or nearly-white DMT would be best for this, because yellow DMT could possibly deliver a progressively weaker vapor after each toke.
I don't know exactly how true this is because I've only made a DMT cartridge/vape once, and it was with white DMT crystals. It works perfectly fine.
I do a 1:1 ratio when combining the DMT with the PG. I used a basic weed pen battery (Eleaf Mini iStick) with a 1 gram (1ml) refillable cartridge.
For the Juice, do the following:
Measure out 500 mg of your DMT and put it into a small mixing vessel. Then add 0.5 ml of PG and mix/stir with something like a toothpick for example. Stir it every 15-20 minutes for about 2 hours total (No extra heat is needed). This will give you 1ml of juice to use. Then use a blunt-tip syringe to put into the cartridge. The mixture should all fit into the 1 gram cart.
If you're about to vape the cartridge, shake it well before heating and inhaling the vapor to ensure the DMT and PG are mixed together evenly. Adjust the Watts to your preference.
3-4 long tokes should be enough to get you to blast-off for a breakthrough. Remember to hold the vapor in your lungs as long as you can before exhaling. Doing deep breathing exercises before vaping will help with this substantially.
Hope this helps