Tips for Touching Up Walls:
Before using paint – reduce the need for touch up by cleaning the walls first. This goes a long way. Just a bowl of soap and water will work. If you need a stronger product, here are two:
Use spackle sparingly, and it will make nail holes disappear. Fill the hole and wipe with a damp cloth so that there is no excess on the wall.
If you need to touch up the spot just use a Q-Tip with a drop of paint. It will be less visible than a pass over the area with a paintbrush.
If you need to touch up the walls, try to use the same batch of paint that was used for the original paint job.
Use a throwaway plastic bucket with a handle to hold the paint safely as you move around.
Mix some water with your latex paint to thin it down. The light coat will cover, but not be as noticeable as a heavy layer.
If you must have new paint mixed, be prepared to paint the whole wall. Paint swatches that are not matched exactly will not appeal to buyers.