Another way to deal with seams is to use the extrusion or "squeeze" technique. This is useful on parts like Godzilla's legs, left and right fuselage halves, pieces where you've got a long seam.
You hold the parts together and flow liquid styrene cement into the seam, letting capillary action draw the cement in. Then apply pressure along the seam, till a bead of melted plastic is extruded along the seam. When the glue and plastic have cured, you can scrape that bead away, leaving a minimal seam that requires very little cleanup.
I like that method, where I can use it, because the join is homogeneous, unlike joins where I have to apply putty or other fillers.
A similar method is to use stretched sprue to fill any seams. I'll use the kit sprue, so again, it's the same material as the parts. Stretch some sprue, then lay the pieces into the seam, and run liquid styrene cement along the seam. Again, when the glue has cured, it's a solid join of kit plastic.
That's not to say that putty doesn't have its place, either. But it's good to have multiple arrows in your quiver.
Hope that helps!
Best regards,
Brad