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Put bind "mouse1" "+attack;r_cleardecals"

This is something to use to "clear decals" so basically you bind a key you hit frequently for instance shoot, or walk to "clear decals" which gets the blood and flashbang/smoke/fire stains off the walls, ground etc... it will help you distinguish between people against a clean background better, than when there is blood spatter everywhere. The script is this to type in console:
Here is how I did it:
bind "Shift" "+speed;r_cleardecals"
bind "CTRL" "+duck;r_cleardecals"

Basically you can bind whatever key you hit frequently while playing. Please give it a shot and let me know what you think.

r_cleardecals is the command