Time.

I'd just bottle them, shake them daily and let them age for a few weeks.

Fill a Tupperware container with dry rice or lentils and microwave it for a minute or two, until it is hot but not roasting. Stir it first, the center will be hotter than the outside layer. Next, bury your bottles, put the lid on and walk away. The rice stays hot for an hour or two and there is no possibility of rice leaking into your bottle (as opposed to water quick-steeping).

I bring mine to work and leave them in my truck, then shake the shot out of them on the drive home. Been pretty hot latley so it's been working good.

plastic bottles.

I get my faucet water as hot as possible, fill up a Tupperware dish and set all the bottles in there from that mixing session. Let them sit for 30ish minutes, go shake the shit out if them, then dump the water and replace with more hot water. Repeat. Repeat.

I've heard people toss them in the crockpot on warm, but I haven't done that yet.

Throw then all into a plastic bag and then put then in a crock pot full of water and then set it to warm for like five hours. Does amazing things

Transfer to glass soon. But I just heat up a coffee mug with water in it in the microwave. Let it sit for 20mins and it's good to go

Just let it age. If you use heat, add the nic after. The heat will just help it mix better... and you don't want to use too much heat. Just warm bath, shake, and set it in the closet for a week or more.

What xnavyguy said. Shake daily and store them in a cool, dark cupboard or drawer. Slow, natural aging. It's not freaking rocket science!

Now that it's warm, if you're out and about driving just throw them in your glove compartment and shake every now and then.

Then, let them steep in a cool, dark place like you normally would at night.