Hi Sean,
There are as many different ways to hide fuselage seams as there are airplane kits to build. I have two methods that I use. If the seam is really bad, I'll use putty. Putty seems to leave tiny craters though so when I get it shaped more or less the way I want it I'll then use Zap-A-Gap, gap filler and smooth it down by doing a final sanding session.
For probably 95% of the fuselage seams I've encountered thus far, I will simply use the Zap-A-Gap by itself. I like to apply one coat of Zap, let it dry and then apply one or two additional coats. This builds the seam up higher than the actual fuselage. It also allows me to take off what is needed to fill the seam but maintain the original rounded shape of the fuselage without flattening it out. After all the filling and sanding is done I apply a coat of primer to pick out any small details that need further attention. If all is good then I rescribe any panel lines on the fuselage that were distroyed during the sanding process.
Hope this helped ya a bit.