Hey! This should be a fun build to watch - great choice.
The rubber bits will take paint ... but won't hold it under much duress. I've had some luck painting then sealing with something like Testors Dullcote. But the finish will be fragile as you can imagine.
What I do now, following the example of much more experienced ma.k builders, is to use green stuff to simulate the rubber parts. I use armature wire through the joints then sculpt the green stuff over the wire and into the joint cavaties. You lose any pos-ability (sp?) but get a realistic "rubber" look that will take paint like a champ!