I just flip my bike upside down, use a marker and the brake pad as a reference point, then spin the wheel and where it touches, it's where it's bent too close in that direction.
Every 6-9 months I'll spend an hour or so watching tv and carefully truing and tensioning my wheels. I can then go for the next 6-9 months with my tires at max psi through NYC streets with all their potholes and trash without having to worry about it.