do you still do one large one as a base and then trace small lines over top of it or form a large line just by doing really small lines?

If it is an auto, i think you need to have the bike at a certain angle with a certain amount of momentum. I am definitely not the guy to ask about this, but hope I could help

Start with the rider moving in the direction of the line you will make. The rider should be leaned back so that if you only have a single line, he will lean back too far and die. Place a small line over the already existing one. (this may require many adjustments) When the rider hits the beginning of the second line, it acts like a little bump that makes the rider lean forward a little bit. Start another line after the second line to make the rider lean forward a little more. THE RIDER MUST ALWAYS LEAN BACKWARDS. If the rider leans forward, any bump will make him lean forward more, and the wheelie will end. Keep on adding small layered lines at the right spots so that just before the rider leans back too much, it hits the "bump" and leans forward, but not forward too much. If you have a gravity adjustment such that the rider always moves along the line, you can theoretically make an infinitely long wheelie line. I did this in my track https://www.freeriderhd.com/t/455199-plain-and-slow