I used 20 cent australian coins which are exactly 28mm in diameter, and sanded the edges smooth (Australian coins are ribbed, for her pleasure one can only assume). A bit of grit and superglue and Bob Monkhouse is your uncle- a mould master for 15 bases. If I pull two moulds from this I can demould 120 in an hour.
Yep. That should just about do the trick...
So how do you chip- proof washers?
Buggered if I know, I am not psychic... but let me tell you how I chip proofed mine.
I varnished them with superglue.
Yep, dab on a little cyanoacrylte glue and use its nylon nozzle to smooth it out around the edge. Let it dry for ten minutes and apply another coat. After a couple thin coats you end up with somewhat uneven and rounded finish, but nonetheless a tough shell over your paint coat that will survive gameplay. You can then paint your top coat over this, and I suppose varnish as usual.
I put black electrical tape under mine, to fill the hole and tidy the undersides up a bit and act as a protective cushion against scratching tables. I did this before the superglue, which ties it all together like The Dudes rug.
Its not as neat as resin bases, but is a solution to the problem.
If you have any tips for paint and washers, love to hear it!