I've had good results using cheap B&Q sprayers with hydrochloric. Like Roger says, make sure you release the pressure whenever your not using it. I usually give it a good swill out a few times after use, then fill it up and pressurize is, then lock the trigger on and let it empty while im packing up, this way, you also rinse off all the trigger/hose/lance and seals with fresh water. I've had a good few months out of them using acid.
Not sure about wfp brushes, but most block brushes from the big sheds can handle hydrochloric. im assuming a stiff bristle cill brush would be ok with the acid. The ones with the plastic type bristles..