This sounds familiar--did I see this question from you somewhere else already?

Try using putty and a razor saw.  That was Shep Paine's tip to us, back in the day, in the old "Tips on Building Dioramas" brochures in Monogram's armor kits.  He used spackle, too, back in the day.  Apply the putty/spackle to the surface, then use the razor to make the rows/lines.  Use the tip to do the vertical lines, and then hold the blade vertically and drag the teeth through the modeling mass to make the horizontal rows.  It works pretty well, and what I like best is that it's frugal--you probably already have a razor saw and putty, so you don't have to shell out for Tamiya's purpose-made, single-use tool kit.

Hope that helps!

Brad