Your absolutely right about the minimal solution volume required. I became curiously aware of this when using my one shot pyro solution and seeing first hand the efficient coverage gained by the brush method. Here are some additional thoughts that I hope provide some thoroughness and practical application.
TRAY CONSTRUCTION & SET UP:
I've included a few snapshot pics to illustrate my very basic tray set-up. The 8x10 tray pictured is clean, but well used and stained from frequent use over the years. I've divided the tray into two sections for 5x7 negatives and I have a separate tray for 8x10 use, and another tray with four divisions for 4x5 negatives. I would normally have two gloves on and no watch as seen in the attached photos. I have included a pic of the spiral wrap material which was cut to size and used for the tray divider. I simply used an epoxy glue (in this case, Liquid Nails adhesive worked well). What I like about the spiral wrap is that it allows some flow of liquid through the spiral material while keeping negatives separate from each other. One can really customize this material for it bends and can be cut to any size.
PROCESS METHOD:
In terms of processing technique, I don't really worry about precise rate of speed or the counting strokes, but establish an acceptable pace with consistency. I just set a countdown timer for 8 minutes with my Tri-X in 72ºF dev. solution and slowly and gently (systematically) brush from left to right two complete times over the negative, then move over to the other negative on the other side of the tray and repeat the same process. During this time the opposite negative is resting in the solution as the developer works toward exhaustion. Then I go back to the other negative and continue until my time is up. I also enjoy a metronome which I use for many things. I find this method immensely creative and satisfying which is one of my chef ways of encouraging consistent and repeatable processes. If one enjoys something they are prone to do it again, and to do so with dedication, as a habit that serves them well.
FINAL OBSERVATIONS & TIDBITS:
If one assumes a 6-12 minute development period with most developers and film, sufficient passes and coverage over the negative are almost assured with uniform development. Some photographers will brush in different directions (cross strokes) which is fine, but I find that brushing parallel and toward myself works well with one hand free to gently maneuver or navigate the brush over the film. My free hand is never head on the film in one place for long and is always applied gently if at all. One finds improved dexterity with repeated experience.
While I generally use TXP 320 or FP-4 Plus film, even using the very soft emulsion of Efke film will not scratch this way. I find scratches to occur far more easily when the film is "sloshing" around the tray hitting everything during general methods of agitation or when floating around loosely along with other negatives during careless rinsing. (scuffing each other) Thus, the value of common sense and perfected use of repeatable "good" habits.
By brushing the film properly one will almost assure no air bubbles being trapped and extremely even development, unlike what can be a problem with general tray agitation if not done with care. Don't get me wrong... normal tray agitation is just fine, and some photographers might want to do a combination of agitation and brushing as well.
I am sure others have different or better methods, but this has worked well for me. I am currently doing this method almost nightly for a commissioned historical documentary photographic project involving the relationship of historic architecture and urban culture in Seattle, Washington. So I am taking great care in my work and place full trust in this method, particularly once one has a little practice in place.