Had them hit our house last autumn and found them harder to shift from my daughter than my son. Tried the mousse rather than a shampoo with varying success and found the Vamousse one worked well for us. Plus it had a game you could download to a phone to occupy the kids when applying it or combing!
Invest in a good comb and do that regularly as that helps clear out the crap. Apparently shampoo containing tea tree is good as nits hate the stuff. Also apply conditioner then comb as it sticks to the nits and lice allowing the comb to get it all out