Last year, when my dd was 5, we did the brushing protocol with her. The behavior changes were quick and obvious. She was a nightmare! Acting out, acting obnoxious, increase in tantrums. Clearly it was having an effect on her, but not a welcome one.
She liked the brushing, asked for it. Immediately after being brushed, she would feel good and be calmer. But, overall her behavior was altered for the worse.
Her OT said that some kids have that effect. It means that the brushing is doing something, even if it's not what we want to see. We stuck it out for the whole time, then stopped, except occasionally using brushing as a part of her diet, but not the protocol. It did seem to have a lasting effect, though. Lots of her behaviors related to her spd just vanished, and she did have some significant leaps in her learning.
Dd is sensory seeking, so this might have something to do with it. I've heard that brushing has less predictable results with sensory seeking kids. Based on my experiences, though, I would do it again if necessary. The results were worth the torture. The behaviors did ebb and flow, but they didn't go away the whole time. We stopped brushing regularly, and within days, she was back to her sweet self again.