Chameleon add-on for Firefox, randomly rotates your browser, OS, screen size, timezone, device type, language, and other customizable parameters every x minutes.

I've set it to do so every 5 minutes, and to omit desktop & tablet as device types (else some websites display the respective page) and timezones (messed up 2FA).

I also disabled blackberry and windows phone from the manufacturer ID, that would have the opposite effect from obscuring me.

For the rest of it, it's working great.

Tell me how, then, because I don't know how to get around the font thing. Everybody's computer has a different set of fonts, and blocking browsers from seeing what fonts you have installed would help identify you even more.