Check your suppliers like Brenntag, Univar, etc.. and you can get the 50 pound bags from$18.00 to around $50.00 depending on where you live and the supplier.
It is usually sold as a powder, not as a liquid. Try to get the powder....why pay for water?
Don't get this on your hands as it is also a POISON, wear the rubber or nitrile surgical type gloves when handling it.
You can use it in a pump up sprayer but if it is not mixed real good, the clumps can clog the pump up sprayer.
A lot of guys X-Jet it or downstream it for larger areas of concrete.
I tried it here and did not have any good luck on the fertilizer stains, brightening concrete or plain old rust stains. It could be my environment or maybe the product was made weak? Others around the country have had good luck with it. For the price, I would give it a try and see what you get.
Good Luck!