Okay. First putty can be a relatives visit. A little goes a long way. First try looking at the seam before you glue. A lot of times seams can be seriously reduced by trimming or light scraping before you glue.
Next using liquid cement try to clamp the parts together tightly and if a little glue come up when you scrape along the seam line (use the back of the blade), that should eliminate the seam line.
If not, put masking tape down along both sides of the seam. This will protect other details. Use very little putty and see if that helps.
Now here is a trick I learned while building some Aurora figure kits. These kits had seam lines big enough to hide another kit in. Putty does no good on the surface, so using the back edge of the hobby knife, I would make a very small v groove on the top edge of the two pieces.. This will allow you get the putty into the seam and you can then use any putty to fill it in and get an invisible seam line.
Good luck
Bob Gregory
Ruining one kit at a time.