I have Cabots clear solution on my half log siding, but on the south side where sun hits it the knots turn white and stain soaks into wood. I stained it 2 years ago and it looks bad again, the rest of the house looks fine and was done some 5 years ago. I was told to put shellac on the knots then stain. How about the wood area that is dull where stain soaks in, do I shellac them too? Is shellac the best or is there another solution. Thanks