Tool needed is the spary gun and Air compressor
NO.1 and NO.2 is NOT GOOD for sparing the coating agent/liquid
NO.3 is the best tool for sparing the coating agent/liquid
About the spary gun, the smaller diameter(the nozzle), the better
About the Air compressor, 1~2L is enough (or a little bigger)
How to spary ?
Adjust the aperture of the spray gun a bit smaller, and increase the air pressure a bit, sweeply spray 3 to 4 times evenly. So, it will need less than 1 mintue to dry usually and it will dry very fast after printing and will not fade from color
The performance of the right spray is that the spray is foggy, not water droplets.