How many of you remember what a fly sprayer was? A small 1qt tank with an aspirator on the top and a pump cylinder sticking out opposite the aspirator. A hand pump operated the cylinder.
You filled the tank with DDT, pointed it in the direction you wanted the spray to go and pulled the plunger out of the pump and pushed it back in. On the forward stroke, air would exit the aspirator and draw liquid up from the tank and spray it.
I once saw an old Mexican spray painting his car with one of these. He was getting the job done too. This was way back in the '60s. Before cell phone cameras or I would have taken a picture.

 

his truck still looks better then mine does ....and he is doing something I can't ..body work and paint...what's the masking tape for ???