You need an electric heating pad and a microfiber blanket a warm towel and a hair dryer will work in a pinch but that is back again to pretty constant monitoring and attention...also the will keep warm based off of the warmth of the milk it's really difficult there with kmr as you dont want it to be above 118°F or you risk scalding their mouths and then they wont eat so...
If you have access to fennel fronds (the top wispy leaves and stalks of the fennel plant not the root bulb), raspberries and raspberry leaves from the plant, or plain rolled oats (oatmeal) you can try to feed Mama those to start her milk production. Some does take longer to start than others, and even the same doe having had multiple litters beforehand can have issues if shes stressed or underfed. She should be free fed high quality pellets and lots of hydrated veg right now along with her hay.
You can mix the oats in with her pellets. You can also feed her Black Oil Sunflower seeds to help with this they're high in fat and fiber and work well. Same deal as the oats.
If you have access to plaintain weed, there are 2 types and both will work, this will help as well as dandelion which is really best. I'm not sure what you've got based on your location but it would have to be chemical free to be safe to feed it to her and well washed, and you would need to gather quite a bit of it. Not too much though or so she'll have so much milk she cant get rid of those both work really well about half a cup and she'll have milk in a few hours once the enzymes in the plants are digested and in her system.
It looks like this...
https://goo.gl/images/3FP3zh
https://goo.gl/images/8MsRaD
You can also massage her belly rubbing and gently kneading across her nips to stimulate her milk to come in. If she just gave birth though this can be a bit tricky depending on how close you are with your Doe and how sensitive they are for her at the time you do this.
You have a very short period of time where you need to get them to nurse from Mama to get the colostrum which is only present for the first couple of days after birth.
You can purchase some freeze-dried colostrum online and add that to the kmr/half & half formula, but it's probably not going to get to you in time at this point. Really just work with Mama and do what you can to get her milk production going and try to get them to latch to her the suckling can stimulate her milk glands as well.
Make sure they're warm before you encourage her to feed them. They'll feed 2x a day off Mom more off replacement formula.