Giles,
Funnily enough, I stopped using Humbrol enamels because the "red" reds never gave good enough coverage on black-undercoated 15mm figures (though they did have a wine colour - think British officer's sash - that gave a very good deep red for ECW figures). Everyone I've asked about Foundry in the past has said how weak their reds are.
Swampster,
Thanks, I was hoping someone from the GdeB side might have a different method. As you say, size matters! The red oxide I'd been using on 15s looks too brown on 25s - but does do well for Continentals in captured British uniforms.
RtL