If deportation forces aren’t currently swarming your streets that much but might soon be doing more of this (looking at Europe here), consider practicing on cops and public transport checks. How long can you keep a cop busy by arguing about minor things? That’s time he can’t spend harassing homeless people. How long can you try to find the ‘lost ticket’ that was in your pocket all along? If it’s enough to get to the train or bus to the next stop, it’ll allow those without tickets to make an escape and avoid a fine.
Doing this a lot will make you much better at it and will put a little good into the world on a daily basis.