Deseed the superhot(s) and give them a pulse in the food processor. A couple bursts until you have a relish like consistency. Then add to your grind and incorporate by hand without overworking the meat (for burgers). For burgers, I'd avoid any extra binders like egg, you won't need it if this is done right. For meatloaf, par for the course.
If no processor, a very fine dice works. Anything larger keeps the meat from binding naturally so you have pockets where the burger will want to fall apart.