I used some floor varnish I had spare on my router table top and fence, then gave it a quick sand with 320 grit sandpaper on the random orbit sander and now wood glides over it (though that might not be a desirable effect for the radial arm saw?)
I'd give the MDF a coat of something because it might swell if it gets damp. I don't know about Danish Oil sorry.
I bought a tin of 'MDF sealer' from a local place the other day, which is supposed to seal it enough to accept the same kind of paint you'd use on wood... it's completely useless, and produced the same result as one might expect from soaking the MDF in water for ten minutes, with no noticeable benefits when subsequently painting. So don't buy that. ;-)
(I'm having a go with either PVA glue or acrylic lacquer next...)