Yes I follow bad kats recipes for making thc infused coconut oil.
Use coconut oil forsure. I have a piece of styrofoam I dug out more than 25 holes to stick the bottoms of the caps in. Fill em up and attach the top. If your hand is steady enough to bring to the fridge, or your house is cold enough, you can chill the bottoms filled with oil like @Herb Forester kindly pointed out (great idea).
As far as potency I aim for as much as possible trim to oil ratio. I often find not being able to put the ratio I want in, as it is just too dry.
Decarb your bud. Typically 40-50g trim to 1 cup of melted oil. But I have to use about 1.5-1.75 cups of oil to be efficient and cover the leaves. If your using bud you can probable go at 35g to cup of oil. Then process in oven with aluminum foil sealing the top. 220 for about 45 mins. Let it cool, take off the top and give a good mix. Freeze that shit 6+ hours. Let it come to room temp. Cook again 220 45 mins. Let cool to touch. Mix that shit good. Seal up again and process 220 for 45. You want to go to sleep? Cook again at 220 for 45. You dont want to wake up, AT ALL? Cook one more time but for 30 mins.
After processing, put the mixture into a cheesecloth in a potato ricer. Squeeze that bitch.
Make sure to keep the oil liquid while filling, but NOT HOT. Too hot will warp the caps.