As paint gets old it continues to "off gas", that is it slowly lose its solvents that made it liquid in the first place. When this happens you need to replace the solvents. WD 40 is not a bad choice. Most finish restorers use silicone, these can make it difficult to paint over in the future. Add the solvent back until it will not absorb any more, then lightly polish off some of the oxidized paint, then wax.