I found a couple threads but they didnt specifically answer my question so here is another..
if I spray my cake dummy with water and then cover with MMF.... can I take the MMF off in a couple of days easily?? or is there a better way to prep the dummy for easy removal?
Then if I want to use a cake dummy as a center tier on a stacked cake, and my dummy is hollow, do I need to somehow dowel something for the top tier or will the dummy be strong enough to hold up the top tier?? I want to do a 10, 8, 6 cake with a 8 dummy in the middle.
TIA
Have never tried to remove fondant from a dummy, but I think if you soak it in water for a while it should come right off.
As for the stacking, the dummy should be strong enough to hold up the top tier, just make sure you still dowel the bottom tier!
They wash off with soap and water. I used royal icing under my fondant which actually made it a little harder to come off. But you can use buttercream also. The only thing I found with plastic wrap is sometimes it doesnt cling. Try using the press and seal wrap because it works better at getting the shape.
They also have something that is made especially for cake dummies called Perma Ice. Its made so you can wash it off easily. I know Sugarcraft carries it. Not sure who else does.
Water is the best way to prep a cake dummy for fondant icing.
I too looked at the perma ice stuff, but it is kinda expensive and you have to buy special colors to color it and just seems like a hassle to me. JMO!
But I have been told here on CC to brush down my dummy with water and then apply fondant and or brush on piping gel in a thin layer then lay on fondant.
I was told either way you soak dummy in hot soapy water and then scrape off what didn't melt off to clean.
Don't use water. I couldn't get fondant off of my dummy and gouged in a few places. I would use a coating of buttercream then put the fondant on. Much easier to take off.
I think no matter what you use, the fondant is going to get hard anyway and your still going to have to soak it in the hottest water possible. Not only that it takes a long time to get it off and you do end up gouging it in some places. But you can glue the pieces back on or fill in gaps with royal icing.
Let the fondant harden. Then take the fake cake and hit it against a hard surface so it cracks and then just take the fondant pieces off.
Piping gel. Not water. Water gives you problems you just won't have using piping gel. To remove, soak in hot water. Whamming the dummy against a wall to break the fondant will only give you dings and dents that won't come out. And don't use soap in the water either -- just hot water. You can change the water if you like after it gets cold if you need to. Good luck! 
Here are my first 2 dummy cakes and my first 2 wedding cakes in fondant!
http://www.cakecentral.com/modules.php?name=gallery&file=displayimage&pid=573013
http://www.cakecentral.com/modules.php?name=gallery&file=displayimage&pid=573003
Here are my first 2 dummy cakes and my first 2 wedding cakes in fondant!
http://www.cakecentral.com/modules.php?name=gallery&file=displayimage&pid=573013
http://www.cakecentral.com/modules.php?name=gallery&file=displayimage&pid=573003
I took a look -- those cakes are simply gorgeous!!! (Getting out my dummies as we speak...) 
So were they a 10 and a 6"? That's what it kind of looked like to me. I love the elongated pearls too for the border -- was that fondant in a mold? Very pretty!!!
What I was saying about water vs piping gel -- it's been my experience that water has a way of causing the fondant to bubble up and not get that smooth. Now that's not every single time, but it is more times than you care to have. I've not had that problem with piping gel. But it looks like you have the situation well in hand!! Keep on practicing!! Nice work!! 
Yes, the elongated oval beads were a fondant/gum paste mix I used in a mold to save me time. THEY WORKED LIKE A CHARM!
The lady who I did these dummies for wanted a clean, elegant ivory colored fondant cake but couldn't decide on stacked vs separated. She hates pillars and the such. So I made 2 cakes with same basic design and got 2 cake dummy displays out of it. The topper was hers and that's why it is in both pics on both cakes. Not my choice but hey, it's her cake.
I used only a little water rubbed on my dummies and they seemed ok. But I had no piping gel and all stores were closed on memorial day! She wanted to see them today so no time to shop!
Thanks for all the kind words.
Oh, yeah...I almost forgot I didn't use anything other than water to stack my dummies. I figure the nicest one I'll keep up and the other I'll tear apart when it gets yucky and redo it to another design.
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