The same is the case with foam, it soaks up a lot of resin. Apply a "screed" of sloppy/thin bog to the foam before laminating. This will fill the holes and prevent too much heavy resin from soaking in while providing a reasonabe bond for the skins. I don't think this method will work with timber because there are no big holes for the bog to be worked into.

This does depend on the consistency of the mixed epoxy being used and the type of timber. Thinner epoxy will soak into porous timber very quickly, to the point that it looks and feels dry after soaking in for 15 mins. Thick epoxy can leave a glossy painted finish to dense timber.