What are you doing using a scrubbing brush for stain removal?
Brushes are for agitating pre-sprays. For stain, and usually spot removers, you need something much more gentle. For small spots and stains I will use a bone spatula, or steel if appropriate. For larger, I have a plastic Addis scrubbing brush with two grades of bristle (from Tesco etc) I dont use the brush for spotting, but part of the handle is moulded as a scraper, and this makes a terrific tool for gently agitating the larger spots.
The angled front part of the Addis brush is great for gently agitating pre-spray into perimeter draught marks, followed by a repeat with a towel prior to rinsing.
The best brush to be used for stain removal is a tamping brush used over a white towel.
SAFE and happy cleaning

Ken