There is an organic pesticide called Neem oil. It is from some sort of nut I think. It will kill most bugs and is safe for humans. It is used on organic food crops. It will kill them and disrupt their life cycle so the nits don't mature. You can get the oil on ebay.
I recommend getting the oil and mixing it with shampoo. Wash hair really well with that and then use the oil mixed with conditioner to keep hair wet while you comb the critters out.
It is easier on the system than the OTC or rx lice products. It doesn't smell good, but it doesn't hurt.
Do NOT rely on the plastic combs to get the nits out. Get the metal comb set (I got the one sold by RID for about $10 for 2 combs a few years ago) and use that. It works better because the little plastic comb fingers can bend and let the lice and nits slip past them.
I have thank you use a little neem oil in a shampoo about 2-3 times a month because lice hate the smell and it will keep them away.
Barring that, getting the bugs and nits out by combing is really the only way to get rid of them. Sit a child with damp hair down on a stool in front of a video. Stand behind them with the combs and saturate their hair with cheap conditioner. Use lots, adding more each time the hair seems to dry out. Also keep a water bottle handy to mist the hair as needed.
Using the metal combs and a big box of kleenex, divide the hair into sections and comb through. Wipe the comb on a tissue to get the conditioner and lice/nits off of it after every pass through the hair. Keep a garbage bag handy to drop the tissues in. If the fine comb goes through the hair smoothly it is probably clean. If it pulls then you need to keep combing and wiping until it is smooth.
I repeated this daily because my kids ahve about the thickest hair you can get. I once did it without the neem oil or pesticides and the combing worked just as well with-o the OTC or rx treatments. It was MUCH better when I had the need oil, but if I didn't have that I would probably just skip the RID except for the car. I would put pillows in bags or the dryer on hot, and wash bedding.
For us, the OTC and rx stuff seemed to be a waste of $. It didn't work well, cost a fortune and it still took all the labor that using nothing but conditioner and the combs took.
The neem oil meant I only had to do the comb out 2-3 times in a week. No nits hatched and I checked thoroughly.
If your kid has an eyeclops toy they are great at helping you see if what you are combing out is a nit, a louse or dandruff. It entertained Tyler during much of the process. Especially when I would shudder each time I looked at the image on the tv.