1. When doing a burnout or actual pass, never let off the gas in 1st gear! You will destroy the overrunning clutch (sprag). You will have to start your burnout in 1st since you don't have a manual valve body, but get into 2nd and 3rd as quickly as you can and do the majority of the burnout in 3rd gear. Don't overrev. 5000rpm in 3rd gear is plenty.
2. Don't burnout in the water. Roll the back tires through the water and then do the burnout. Technique will differ depending on whether you are using a line lock, type of tire, track conditions, etc.
3. Don't downshift after the pass. Let the motor rev down as you apply the brakes.
4. You can start at 5800 rpm as a reference point, then try different rpm both higher and lower to see what the motor/gearing combo likes the best. Above all, have fun!!