If it is a tight multi-point pattern I sometimes use blue painters tape to mask out the adjacent areas of checkering while I'm repairing or rubbing out an area on the stock. I remove the tape immediately afterward to make sure that any finsh/rottenstone mixture didn't puddle up in the existing checkering and if it's there, remove it.
I use felt pads that I cut to different shapes to reach in and work around checkering and I go very slooowwww...and take my time. The felt pads are made in different densities and stiffness. limp pads are used on the round and curved areas, stiff pads on the flatter areas. They key is to take it easy and go slow,wipe the stock down frequently, checking your progress as you move along. You don't want to cut through the existing finish down to bare wood.Damage to checkering generally comes from being in to big of a hurry and not using the right materials for the job
