The best place to filter noise is right at the source of the noise. I'm assuming you're getting the brush noise from the AC motor, is that correct?
If that's it, I'd consider adding some inductance in series with the brush leads and then the 1uf NP caps. A .1uf cap across the brushes might help as well. This will probably be somewhat of an experimental process, EMI is sometimes pretty unique to individual situations.
