Be sure to straighten and separate each individual branch before painting.
Mask any areas that you want left unpainted.
Set the tree up on cardboard or another disposable surface to paint.
Paint a few light coats on the tree from all sides. Then pick up the tree and paint from the bottom. You should be able to tell which surfaces you are not going to be able to reach from the top.
Set the tree back down and paint from all directions including the top and all sides. Go slowly with this and paint in light coats.
If you want to add glitter paint on top of your color, spray it over the top at this time.
Once you have complete coverage, allow your tree to dry for at least 72 hours in a warm place before moving the branches.