Rapid fire on trigger

[5th-axis]

I was under the impression that Console customs were the only ones to offer rapid fire on the trigger. I was perusing ebay and found several vendors that offer the kit for the trigger with no transistor and the tut I saw made no mention of cutting tracks or anything. I think they were using a 12f629 as well. How is this possible? I would like to figure this programming thing out, but this threw me for a loop!