The kind you get in an automotive store is fine. The “Food grade” stuff for sale (I think it comes in a green can) is too high a grade for what you’re going to be doing with it. Not worth the extra expense. Sort of like “laboratory grade” vs. “reagent grade”. One costs more than the other, but if you don’t need that high a grade, then why buy it?
If you buy one of those “this is how you make candles” books, there’s **** they don’t tell you. Like, don’t shoot the release agent (silicone) down into the mold. It will just run out the bottom into a puddle. Hose down a clean, new, shotgun bore mop with silicone spray, then punch each individual mold. Twice. Punch each individual mold, then move to the next one. When you’re done, start over and punch them all again, just to make sure.
Preparation will take up most of your time – making sure the wicks go directly down the center of each mold. Some candlemaking supply places sell this stuff that looks like PlayDoh or Silly Putty. It’s used to clog up the wick hole at the bottom of each mold. Also, some gang molds have separations at the other end of the mold and might leak. Use this PlayDoh stuff to stop those leaks, too.
I usually take a propane torch – on low – and play it over the wax in the mold as the candles solidify. See, as the wax cools in the mold, much like metal cooling, it shrinks. Which means you use the top of the gang mold as a reservoir.. As the wax shrinks, it will draw on that reservoir of melted wax to fill in the gaps… otherwise, you will have hollows inside your candles. Not good. So, I use the torch to make sure it stays liquid.
Some folks put the cooling molds in a refrigerator or freezer. Don’t. It usually ends up cracking the candles.
Let the molds cool fully – go do something else, or prep your next gang mold – and then you can use the connected wicks to pull the candles out. If they don’t come free reasonably easy, don’t pull harder. You might pull the wick out of the candle. If a candle refuses to budge, take your propane torch and play it gently over the mold in question, tugging gently on the candle.. it will pop free eventually.
Last thing is no matter what you use – small, individual molds, gang molds, whatever – use an old cookie sheet under the mold. You will spill wax. If it’s on the stove, the pan will catch the wax and when your wife finds out what you’ve been up to, nobody has to die.
Anything else, just ask..
The wicked flee when none pursueth..." - Proverbs 28:1