It was GW Decals i used for that. Although my freehand can be decent in placed im no where near that good, yet
The yellow strip is to denote battlefield role. Characters and troops are a smooth black base. Elite is Silver/ Grey strip (im undecided as of yet) Fast attack is a red line, and Heavy Support being Yellow.
I did used to do full base rim colours but i think the lines look a lot sharper and crisper, plus offers uniformity