alexy wrote:
At the very least, buy an aerosol can
of Kilz or BIN oil-based primer and spray just the knots before
brushing on your latex primer. I can't imagine a knot bleeding through
shellac + oil-based primer + latex primer + latex topcoat!

Not to nitpick, but I think it deserves to be mentioned that there is no
such animal as "BIN Oil Based". Zinsser does indeed make an oil based
product, but BIN isn't it. BIN is shellac premixed with white pigment.

Details: http://www.zinnser.com/subcat.asp?CategoryID=1