For sprint tires, I found that Hot Lap 2 worked really well. Did not drop the duro too much but provided a lot of bite. For really softening harder YLC/Dunlop SL 4 type tires, Bondatti winter green is the best.
Hot Lap 2 worked the best. We used a wax applicator pad to wipe on the coats per the directions. I believe if the race is on saturday, you wipe 3 coats Mon and 3 more Tuesday making sure each coat dries before putting on the next. Works really well as long as you get the seal off of the outside either by resurfacing them or using Pro Blend tire cleaner. You will need to repeat each week you race.