bobH yeah I only use the canned goo because its the fastest and I get no irritation with my mach3s. I have a dovo 5/8s and have had it for about 10 years and I know it can only do 1 pass and then you need to reapply whatever product you have on that area, with the mach3s you can make about 5-6 passes without noticing it though (at most applying more water).