I've been using one similar to this for about 10 years:

http://www.northerntool.com/shop/tools/product_200578564_200578564

It does need some customizing. The way that the sprayer mounts to the drawbar of the atv was a joke. It lasted about a year before I junked all of that and mounted it to the rear basket. I haven't had a problem with that part since doing that.

If you need agitation, don't buy their kit; its a waste of money. Somebody on here told me how to put a livewell pump in the tank and drill a hole in the top to run the wires to it. That works great and gives you plenty of agitation.

Also, buy a bunch of extra Y cut-off valves. They won't last and will need to be replaced often. They are cheap, so buy several of them and have them ready.

Its one of the most used pieces of equipment on the farm.