I like to mist my trays as they are germinating or if the seedlings are tiny. It (misting) also is an easy way achieve good soil contact for tiny seeds that are surface sowed, like impatiens. I do bottom water my trays, so I use a watering can as well.
I find that the best place to store the water is on top the light fixture. I top up after each use and let the fixture "warm" it up for next time.
