Here are a few simple tips.
I let my thumbnails grow a little longer,they are perfect to use for throat punches or a quick poke in the eyes.
Learn to find a few pressure points and focus on those.
The best way still is to avoid a fight.
A guy i used to work with was a top bodybuilder in Holland and in the weekends he was a doorman in Amsterdam at the IT,he stopped doing it because he found people on certain drugs don't feel anything,they are like zombies.
Again,avoiding a fight is always the best.