go over it once from about 10-12" and leave it at that. you don't want the entire thing to be soaked for sure. all you'll accomplish w/ that is restricting air flow.
if you spend more than 8 or 10 seconds covering the whole thing (while kind of rotating/twisting to get all of the foam insert) then you're probably putting too much (IMHO).
in other words, if your spray oil is blue in color, you don't want the the entire foam part of the filter to be solid blue - if you get that far you probably have too much.
someone else might chime in and tell you otherwise - that's just from my experience.
