I use a technique I've used for rock chips on cars that seems to work pretty well on bikes.

If the paint is even slightly thick, first thin the paint slightly with thinner. Using the pointy end of a toothpick, dip it in the paint and place a drop at a time into the area that needs paint. DO NOT fill up the chipped area in one try. Allow the thin layer of paint to dry and then continue to layer up the paint - thin layer, dry, thin layer, dry - until it is just proud of the area surrounding it.

Give a couple of days for the paint to totally cure.

Take a tiny piece of sandpaper and attach it to the eraser end of a pencil with glue. Use the pencil sander to sand the paint back to the level of the surrounding paint. You will probably have to follow up the sanding with a Scratchx type compound and then wax.

It is an extremely time consuming task to make it perfect.