I saw an episode of Ace of Cakes that they built a wood base for a motorcycle. I'm not sure how else you could do it and get the true look of a motorcycle, but I've never done one before! Good luck, I'll be anxious to see your results!
Water should work fine! Just use a paintbrush and put a line of water on the back edge of the rope and attach to the cake. You may have to do a little at a time and hold it in place for a few seconds for it to adhere.
I have a Paasch, and love it. Have never had any trouble with it clogging, like I have read on other people's posts about other brands. It's great. I think I still have the link from where I bought it if you're interested! Good luck. Airbrushing is a LOT of fun!
As soon as I read the title of your post I pictured a cake that looked like a big vat with fog/steam pouring out of it, and a fondant figure of a "mad scientist" leaning up against it. I would use dry ice to create the fog effect.
I just made a strawberry cake and used the strawberry buttercream recipe in the recipes section. It was very good. Made a LOT of buttercream though, so you might want to cut down the recipe if you use it!
It used to bother me, but now that I post my cakes on CC and FB I get a lot of positive feedback, which is really what I am looking for. It's just nice to hear you've done a good job after you put so much time and effort into something.
You can get some supplies at Michael's Crafts or Hobby Lobby. Also Walmart has a small selection. I would love a better option though. I will check out the ones you listed. I live in Westfield, so I typically go to Michael's and order what they don't have online.