Depends on the surface to an extent, RC glossy tends to show the spotting much more than say a semi-matt.

I have only ever used Tetenal spotting pens which are very good on small spots and the spotting tends to disappear after it has been applied for a while but certainly gloss is by far the most difficult surface to spot.

Most viewers who aren't looking for the spotting would not notice. Trick is to spot lightly and use a pen whose shade is slightly lighter than the surrounding area. You can always go darker and apply more.

Good as they are, I'd do almost anything to avoid the need for spotting in the first place.