I know solvents are popular for thinning out mixtures, such as thick paints, but between coats you wait a few minutes to allow the solvents to evaporate.  The idea is to just thin out the resin/paint long enough for you to apply it where it needs to be (through a paint gun, or into a crevice) but that it is completely evaporated by the time the epoxy mix cures.  In the case of infusion, I don't think the solvent will be able to evaporate from the mix (most definitely not completely or properly at least).