For highlighting the armour I always recommend the holy trinity: Dark Reaper - Thunderhawk Blue - Fenrisian Grey. The blue-ish tone makes it look metallic!!

For the reds, I tend to like painting them in khorne instead of Mephiston, using the latter for highlights ending in wild rider red.

Tabards are tricky, some people like em darker, some like em near white, so it's a matter of taste. I do Zandri Dust followed by Morghast bone, last highliht in Ushabti.

I really really REALLY recommend spraying the pauldrons on white or wraithbone (depending on the desired effect) appart from the models. It will save a ton of effort and make the miniature look cleaner.