I have new douglas fir window frames throughout the house to stain and protect. The surfaces are interior (outer surfaces are painted) but when windows are open, of course they are accessible to rain etc. until closed again. I will be using an oil-based 'wiping' wood stain. What is best to apply on top? The main option under consideration is oil-based varathane. An alternative that was suggested would be to mix the stain with varathane as well as turpentine (33/33/33) and apply that with a foam brush. Any comments or other ideas would be welcome.