Its super easy! Here's what I did last time.....I added about 6 ounces of trim to a crock pot, I then added a half gallon of VG and turned the crock pot on low. It seems really thick at first, but it will thin out as it heats. I stirred once or twice an hour for about 6 hours. I turned the crock pot off and let it sit over night. I turned the crock pot back on low and let it heat up until things got thin again, at this point I strained the mixture through a fine metal strainer, using a rubber spatula to press the trim into the strainer to get as much VG as I could out....I then put the trim into some cheese cloth, and squeezed the ever livin' sh*t out of it, to get the last remaining drops of VG out. BAM! That it. I use it as a tincture, or you can add a flavoring to make E-liquid....you can use PG to thin it out a bit, or if you don't like the throat hit of PG, use a few drops of distilled water.
If you want to make a smaller amount than a half gallon fill the crock pot with water, turn on high (to start), put your weed and VG in a glass mason jar and set in the water bath. My crock pot maintains about 200-205 on high, full of water....but some will go higher....just play with it a little. Warning.....there will be a strong odor.