Anytime I've ever used them I just soaked them and stuck the clones in, with no problems.

On the lights. Of course HPS is much better than MH for the flowering phase, and the more the better as far as its power is concerned. But, the 600w is gonna put out more heat, and in a small confined area you will want to make sure that you have a good ventilation system (even with a 400w), so just make sure the girls don't get too hot.

sn