You just have to get a plastic pump garden sprayer and spray the muratic acid on with it and then rinse very well. I just use it at full strength.

I agree with the Muratic acid. What I would strongly suggest is using a "good" powerwasher, which would have around 2500 psi and 5 gal a minute flow rate. Don't even waist your time with a 3000 psi 2 gallon a minute home depot special. Then use a roto-tip nozzle, it will rip that stuff right off. I've been using a this combo with hot water to remove the bottom paint on my Formula. I've taken about 45% or more off without any chemical at all..

In theory I agree with your suggestion.......However, before you posted this idea I was already one step ahead of you. I diluted some Muriatic acid into a spray bottle and began to spray on a small area. Even if there is no wind, where I am at, the air is still moving. Ask me how I know this. Thankfully I had safety glasses on, but I ended up with a light mist (didn't even feel it hit me) of the acid on my face. If it burns your hand immediately, you can only imagine what it felt like on my face. So given this, even if I was on the other side of the slight breeze, it would be carrying the acid to other peoples boats. So I am going to skip the spray bottle and stick with a brush.

The pump garden sprayer really does not create fine mist like a spray bottle will. You could also use a something like a sponge mop on a handle or paint roller.

we just did my 311 to remove stains and after the acid wash compound the bottom and then a coat of quality wax and let the wax stay for overnight before wipe down and then another coat of wax ..... the acid seems to open the pores in the gelcoat and letting the wax sit lets it soak up into the gel ....

I will try the garden Pump sprayer, as your right it won't create that fine mist. (I didn't read your post correctly. I saw plastic sprayer and after my face burning immediately rulled it out).

get a garden sprayer and do a 50/50 mix with muratic acid and have another small spray bottle with straight acid in it for the tuff spots.Use bondo plastic scrapper and try not to use the razor knife because it cuts the bottom. The bottom is going to have to be sanded and buffed when your done. I hope for you that velocity used some decent gel coat or you will be reshooting the bottom.

I have had to deal with that growth before, scaping/sanding is about the only thing that seemed to work for me....its a pain

Believe it or not, a garden hoe is the marinas tool of choice for removing barnacles such as those. Just knock the corners off the hoe with a grinder so as not to gouge the gel.

or a large drywall knife, but what is left is what you have, in most cases on slow big boats they just leave what you have left and paint over a relaunch...going to take some serious work to get it back smooth again..that crap is unreal tuff !! good luck Rob