How to overwrite brush "texture" with single color in Illustrator CS6?

Question

I'm creating symbols using custom brush packs that I downloaded. Most of these brushes have many different colors in them ("textures"), not just a single one. My question is how to dismiss these colors and, using the outlines of the brush strokes, fill that brush stroke/shape with a single color instead.

I know this can be done with Expand Appearance and then changing the fill color, but that doesn't seem to work for me:

This is a close-up of one of the brush strokes for one of the symbols I'm making:

Here's what it looks like after using Expand Appearance:

If I then change the fill color, I get this:

"No biggie" I thought, "I'll just add a slight stroke to cover that up". Except then I instead get these spikes of doom everywhere along the brush strokes (and it'd take way too long for me to manually clean it all up):

Thankful for all the help I can get!

Answer 1

After changing the Fill color, Use PathFinder > Unite.

If you need to add a stroke to cover things... Setting the corners to rounded or adjusting the Miter Limit on the Stroke Panel will traditionally remove the "spikes."