You may want to use the heat gun to dry the ink of the stamped image well. This is not necessary, but it help with bleeding when using black ink. Also try a grey ink or Staz-ON ink.
1st-Fill your waterbrush with water, and squeeze just a little to get the bristles wet.
Here is how I use the ink-with the lid closed, squeeze a few times.
This should get some ink on the inside of the lid. If it doesn't, you may need to add some re-inker to you pad.
With a wet water brush, pick up some ink on the bristles
Depending on the look you want, you may want to squeeze out a drop of water for a softer look. Just remember, more water=lighter/softer color along with the possibility of flowing out of the lines. My tip-practice on a scratch paper 1st. I tend to like the bristle a little dryer, for more control. But there are instance where a really wet brush and outside of the lines looks stunning.
Start slow and in the larger areas. Once you have it colored let it dry completely before adding anything like glitter or chalk or even gluing it on to your project. Wet paper can get a hole or tear really easy.
I clean my brush after each color, and I clean it on the double scrubber. By lightly rubbing it on the cleaning side while squeezing out a little water.
OK-here it is. Now go use your waterbrush, and post a link so I can see how you did.