I have developed a pretty solid technique over the years:
I found that puttying /sanding obliterated adjacent panel line detail and other belly features which unless re-scribed, was unacceptable.
I use micro thin styrene rod or stretched sprue to fill the gaps. I try not to use ANY cement or putty. I simply "press fit" the thin rod or sprue rope into the joint. Then using a hair dryer on low heat, slowly and carefully weld the sprue into place with heat.
Then using a sharp exacto edge, gently scrape the seam flush. Many times, no further treatment is needed. To eliminate any evidence, a ultra fine sanding stick can be used to gently dress the cooled joint to a mirroe like finish with no evidence of transistion:
img.photobucket.com/.../hell4.jpg
img.photobucket.com/.../P409.jpg
img.photobucket.com/.../F4F5.jpg
img.photobucket.com/.../spit3.jpg
good luck
Steve