Do you have a 3pt sprayer?
I zip tied a cattle back rub wick right up under under the spray heads on the boom of my small 50 gal sprayer. I run the sprayer so it soaks the wick really good to the point of runoff, then shut down the sprayer. Reapply the chemical to the rub as needed in the field.
Works really well, and only cost me about $25.