How to get dried plaster out of floorboards?

I recently had 'workmen' in to do some re-plastering. They managed to tread plaster into my stripped floorboards, and to splash it on to stripped skirtings. (All sealed with matt varnish). Of course it has found it's way into all the grooves, old worm holes etc. Short of stripping the floors, is there any way to remove it? Water just seems to spread it and when it dries it comes back. Thanks in anticipation!