1, there are metal combs you can get. KP24 make one. Its not like the usual nit comb. The prongs are wider, round & very close together. Get one.
After a treatment, when the hair is wet, with or without conditioner, use this comb. It will drag out the eggs, as well as the teeny tiny nits the regular combs can miss. If the hair is dry, the comb will pull, specially if it is pulling eggs off the hair. If wet, the eggs will just slide off with the comb.

2, spray all of your heads every day with a mixture of lavender, tea tree oil & water.
This has worked for us. When I remember to spray them every day, the bugs stay away. If I forget for a couple of days, they are back!

These are the only 2 things I bother with now.
Of all the chemicals & things you can try I find these are best to keep on top of things.
If they are infested (happens on occasion ) I get the cheap pyranel foam & leave it in over night. Its only $8 or $9 a bottle, & they've not survived a full night of it yet. Everything else I've used I'll still find the odd one here & there alive after.

Good luck. They really suck!