What's your go to trick for crispy chicken in a stir fry type setting?

I don't know if this technique is applicable to stir-fried chicken, but Serious Eats recommends baking powder: http://www.seriouseats.com/2016/10/how-to-get-crispier-chicken-turkey-poultry-skin-with-baking-powder.html

You'd have to sear/cook up the chicken first, take it out of the pan, then make the stir fry, and then add the chicken back in at the last second. (Check out Nom nom paleo's cracklin' chicken).

Per Sam's comment you are going to find it difficult to crisp chicken just by stir fry.

Get Popeye take out chicken nuggets. It takes all the work out of the frying stuff mess.
Failing that...get a good crunchy chicken nugget thing from the freezer section...not those pasty 'kids meal' type disks..but some with some texture on the outside. Oven bake or fry them.

Otherwise...you'll be spending most of the cooking process trying to get crunchy chicken nuggets. I've done it..and spent too much time doing it.
When eventually...well screw this...bag of nuggets in the freezer, and spend more time on the other bits of the meal.