Monty, you can try super blonde shellac to pop the grain then top coat that with a super clear finish such as Target’s EM9000. I am certain there are other super clear water based top coatings, but this is the one with which I am familiar. Water bornes are the only option IMO because any oil based product will cause the wood to darken somewhat whereas WB products won’t. As always, test your entire finishing schedule on scrap before attacking the completed project. HTH

http://targetcoatings.com/products/interior-top-coats/em9000-super-clear-interior-polyurethane.html

-- Art