How to subtract weight from hair particle weight painting?

I am wondering if there is a way to subtract weight from hair particle weight painting, thanks. All I seem to be able to do is add until it’s all red, then nothing more. Thanks for any info.

Seems to be an issue with using the Hair Guides script, as turning down the strength does allow hair to be reduced in weight, but not the tips of hair created using the addon. Possibly simply a limitation of a WIP.