When I deep clean the brushes, I clean multiple brushes simultaneously with either my beauty blender cleanser or baby shampoo along with lukewarm water. I rub these on a Sigma glove (you'll see a snippet of it somewhere down below) to help with the process (go to www.sigmabeauty.com and you'll find these cool gadgets in their Brush Care section). You can use your hands but I don't because I have dry skin.
After rinsing, I lay my brushes flat on a clean towel. If you store them upright, the water will ruin the ferrules (this is the metal or plastic piece connecting the brush hairs to the handle). You'll risk these pieces rusting or even cause loosening of the brush hairs. By laying them sideways, you alleviate these issues.
Now for the really dirty brushes and sponges...these are the ones where your usual cleansers just won't do. See my examples below:
QUICK TIP: If you have really dry hands like me, I recommend using latex/latex-free gloves to protect your skin.
When ready, roll the brush or sponge into the concoction and coat the surface with a nice, thin layer and start scrubbing (for brushes) or rubbing (for sponges), working the formula in.
I hope you're able to find this information helpful. Try this on your brushes/sponges and let me know how you like it!