assign your beats to an fx channel, or preferably rout them to a bus channel. For example, select your kick channel on the mixer, and right-click on an empty channel send button, the little arrow in the bottom of the strip and select "route to this track only". Do the same to all your drum channels, route them to the same mixer channel. Then assign fruity free filter on this channel, right-click on cutoff and select create automation clip. This generates a straight line in the playlist window that you can redraw to create a cutoff envelope.
Is there anyway that you can link a few mixer channels up. I have all my percussion in separate mixer channels so that i can EQ them all separately, how do i create a bus to put all the drum through a filter at once without putting all the percussion on ONE mixer channel?