This is the kitchen pressurizing sprayer I use to apply an acrylic type aquatint.   I believe it's intended to be used for cooking oil.  You put the liquid in and screw on the sprayer top and then you slide the pump top onto the base and pump it until there's enough pressure.  I do this outside and use a dust mask to avoid breathing the aerosolized acrylic (Future floor polish or Lascaux hard resist).  I stand where there's a darking background so the droplets are visible and I spray up high into the air.  As the droplets fall I slide the copper plate horizontally into the cloud of descending spray and it settles on the plate very nicely.  I do this repeatedly until I have what I want, using a magnifier loupe to check the progress.   Windy days are a problem but I've managed to deal with even that

ot the patience to wait for the weather to cooperate!  I rinse out and pump and spray water through the sprayer as soon as I've finished applying the aquatint.  If I'm worried that some acrylic may have dried on it I put some ammonia in it and spray that but you need to hold your breath in that case.

Here's the sprayer taken apart--the top piece is the pump.  It's a pretty simple device.  There's a gasket you can't see that ensures that the sprayer makes a tight seal and holds the pressure.  I have another one that's all plastic and it has a crack in it but will hold the pressure pretty well in spite of that.

The last photo is of the pump on top ready for pressurizing.

If you look on my Etsy site you can see some aquatinted etchings I made with this process.

http://www.artisanlyn.etsy.com