The Handyman's Pocket Book: Water Stains.

Before applying a water stain the wood should be wiped over with warm water and allowed to dry out. This will raise the grain which can be rubbed smooth again with glass-paper.  Then when the stain is applied the grain will not rise - or only to a limited extent.  It is helpful to add a little alum to a water stain as this reduces any liability to raise the grain.  Oil stains have the advantage of being free from this tendency to roughness.

If when applying a stain with a brush the surface shows brush marks and uneven spreading, you can correct it by going over the surface with a rag damped with the stain.  End grain always absorbs stain more readily than the rest, and the stain used in these parts should therefore be thinner.  Otherwise they will show darker.

Before using a stain it is a help to smear the fingers lightly with vaseline, rubbing it into the nails well.  It will be much easier to clean the hands after staining is finished.