Yes, you can do it. Giobosco pretty much covered the
basics. Adding a tank won't make the compressor any quieter,
however it will smooth out the pulsations and it will probably make the
compressor last longer since the only time it will be on is to
pressurize the tank. When painting you will actually be using the
air from the tank. How long between cycles will depend on how
high the compressor can pressurize the tank (probably only about 35 psi
or so), the volume of the tank, and the volume you use when spraying.
There are two ways you can do it:
The Manual Way -- Just add a fitting to the tank and run a hose from
your compressor. When the air in the tank is low turn on the
compressor and fill the tank.
The Automatic Way -- As Giobosco indicated, get a pressure switch and
mount it on the tank. When the pressure in the tank goes below
the low set point on the pressure switch it wil turn the compressor
on. When it reaches the high set point it will turn the
compressor off. The trick with a hobby compressor is finding a
pressure switch that has high and low pressure cutoff setting that are
within the range of your compressor. If the high cutoff is above
the working pressure of your compressor it will never shut it
off. Likewise if the low cutoff is above the working pressure of
your compressor it will never shut off. Mine turns the compressor
on when the pressure is below about 120 psi and shuts it off at about
140 psi.