Dirt something and count the rounds.
edit: Let me rephrase that. Dirt something, wait for it to rub out, dirt again and count the rounds between the dirt and rubbing out again. I know it's about that long because when I train a 2 round lag skill, I usually dirt, spam it three times, then switch to another screen, switch back for the last hit of the skill, then spam where/who pk/who gr.
