I use Tamiya putty and Mr. Surfacer, also a tip from WM Cheng; use the old testors glue on non-critical seems, if you use an ample amount the glue will squish out and fill in any seems so you have a minimal amount of filling and sanding afterwards.
Also, I find priming plastics more trouble than they're worth since they interfere with the glue process.
Also, it helps to study the plans first and try to figure out what subassemblies can be completed before attaching to other components. The more of this you do the easier it will be for fit and finish of the parts. (example here would be the gear and weels on the model).
Also, go ahead and "collect" that Cyclone model but it's definately not for newbies, trust me on this one. Just put it away in your closet until your skills are up to par.
WARNING! this may be habit forming