not sure what the need for solvents is. cannabutters been doing the job for awile now. and if you want to use a low temp method in order to get "more medicine less high" try NP's coconut redux method. i just did it for close to 6+ hrs instead of only two as is recommended for the vervains.
“If you heat the plant, you will decarboxylate THC-acid and you will get high, you”ll get your 10 mg. If you don’t heat it, you can go up to five or six hundred milligrams & use it as a Dietary Cannabis. . . and push it up to the Anti-oxidant and Neuro-protective levels which come into play at hundreds of milligrams,”