I have an Interlux Schooner varnish question. During my third coat, towards the bottom of the can I noticed a thick, sludge like mass moving around. I can't seem to find any mixing directions on the can, but I know well enough not to shake the varnish to mix it. Should I be stirring the varnish? I'm moving on to my second can of varnish for my 4th coat and I'm curious what I should be doing.