You can get the trees in varied sizes in bags at Michael's or Hobby Lobby , and I'm sure many other craft stores. ( near where the miniatures are)
You'll want a container that is tall and narrow so that the trees can be totally submerged and covered in the water/Clorox mixture.
The mixture should be about 1/2 water, 1/2 Clorox . ( and you can use this same one time mixture for all your trees in your bag) Put the tree in, and watch the process start. How long does it take? Well, depending on the size of the tree approx. 10-15min or so. Just watch, you'll be able to tell when it's ready to come out.
You'll want to use a tongs to remove it.
After you have rinsed it well, dry it with a paper towel and fluff is up a bit.
Set it aside for bit to dry.
Once it's dried for a bit, if you want to add color, you can do this using a number of different methods, but I used Chalkboard Sprays from Tattered Angels, and they worked great. I wrapped foil around the snow base of the trees while I was spraying to keep them covered.
Of course you can made them as light or as bright as you like, by how much spray you decide to add. OR you might like the natural look with no spray, like I did a couple of these. ( you might want to trim off any odd pieces sticking out from your trees)
I liked the look of snow, so I just took some white paint and did a sort of dry brush technique over them. Just all a small amount of paint to the ends of a fairly stiff bristled brush and run in down the tree, all the way around. While the paint is wet, you can even add glitter if you like.
I think I like it.
Hope you give it a try!