You want to look for a Quick Wash Ethanol extraction (QWET) method. skunkpharms research has a good TEK that many are following with success. I've just done a run to make into ejuice.
You want to get all your materials extremely cold--freeze everything at least 24 hours, or even better, pack everything into a small cooler with dry ice (put your herb in a ziploc, but your ethanol in a jar, and place them in the small cooler with dry ice for 2 hours or so, coffee filters or mesh strainer. i use a 25 micron extract bag). put an empty jar with lid in there too.
once everything is cold as balls, put your herb in the cold empty jar and then pour your cold ethanol over it. seal it up and give it a shake. If you're using bud, you can give it an aggressive shake, if trim it can be gentler. For dry ice, because it gets everything so cold, you can do a 20 minute wash (agitate every 2-5 minutes) without too much concern about chlorophyll and fats. For a freezer, keep it to a 3-4 minute wash with agitation every minute.
If you went with the dry ice, just strain through your strainer into a pyrex or silicon dish that is as wide and flat as you can get. cover with micron mesh, a splatter guard or a light piece of wax paper. sit it on a seedling mat with a gentle fan blowing on it. the ethanol will evaporate in 24-36 hours (if you're doing a quart to half gallon amount). scrape up your remains with a razor blade and put into your preferred blend of propylene glycol and vegetable glycerin--i've used 50:50 PG:VG successfully.
If you're going with the freezer method, you'll want to strain the mixture after the 3 minute wash into a jar and place that jar in the freezer overnight to winterize the solution. this will bind up some of the chlorophyll and fats. strain this through a coffee filter into your dish and evaporate, again with seedling mat underneath the dish, a screen to prevent dust etc. getting in there, and a small fan to help it along. scrape up the hash and mix it into your PG:VG mix.
To help the PG:VG mix dissolve the hash, you will want to put your vessel into a double boiler and stir until dissolved. After it's mostly dissolved, whip the mixture to emulsify it. I use a rotary tool with a nylon buffing disc to stir the mixture at ultrahigh speed so as to create an emulsion that won't separate in your tank.
5-7g QWET/ 30mL PG:VG is pretty good strength for me.