I use both dubbing loops while I'm tying and dubbing brushes made up ahead of time. I would second the notion of taking James Smith up on his offer of plans. With his plans and some basic woodworking skills, you can make a dubbing brush tools quite inexpensively. I where a dubbing brush was an advantage vs. a loop is:
a) efficient production tying -- ie, when I need a couple dozen or more of something
b) when I want to do a custom dubbing with multiple materials and especially with materials that are hard to dub -- eg, mixing bits of rubber or flash material with dubbing