I would recommend Biostrip 20. It is pretty awesome and removes varnish as well as paint. It comes in small 500g pots which are ideal for minis (you can get a load done with this amount). It even removes enamel easily. I have used on both plastic and metal, and have been told it works on resin with no issues.
http://www.biostrip.co.uk/biostrip-20-paint-stripper-500ml-tub.html
http://www.biostrip.co.uk/biostrip-20-paint-stripper-500ml-tub.html