Acetone is an adequate solvent for cleaning cured composites prior to
secondary bonding if you use the wet/dry wipe technique. Wipe down the
sanded area with an acetone-wet cloth and then immediately follow with a dry
clean cloth to soak up the disolved, diluted surface contaminants.

I remain concerned about the toxicity of Methylene Chloride, both liquid and
vapor.

Best,

Larry Graves