AWhen I bake my fondant cakes, I bake then the night before, fill and frost. Then I let them crust overnight and prepare the fondant and decorate the next day. I let the cake sit usually overnight or for as close to 24 hours as I can to let set and dry. Most cakes I send off and do not see cut, but a few that were for events I attenended I notice some are very moist inside. The buttercream filling sticks and seeps into the moist cake and it gets sort of gooey. Not bad just more moist than I intend. Ive tried putting them in the fridge until I fondant and decorate, overcooking the cakes slightly so they become more dry..everything! Nothing works. Its when I have to level the cakes before filling, then the buttercream filling goes directly onto open cake. Any ideas or tips would be muchly appreciated.

Are the cakes being cut properly?  A nice, moist cake could only be a problem if the cake cutter isn't wiping the blade clean in between cuts.