Wirraway
Of course there are purists who maintain that you don't need to use putty on seams.
I wouldn't say someone's a purist, if he prefers one method or another to deal with a seam. I use both methods-the "squeeze" method with liquid styrene cement, and putty-Squadron white, thinned with acetone. It depends on the situation. Whichever works for anyone, is best for him.
I also use stretched sprue, or even scraps of styrene card stock, and liquid cement, depending on the size of the seam, or gap.