If you cant feel any ingrained particles with your hand try putting your fingers inside a plastice bag (sandwich bag, cigarette wrapper) and use your fingertips to "feel" the paint work if you can feel bumps then claying is probably required if you want paint that is smooth as glass.

The clay will remove any protection on the paint so you will need to polish and wax/seal the paint for the best finish.

HTH

Scotsbil