The all red looks very RT/John Blanche (that's a good thing). I would paint the extra bits as suggested (horns, metal tips, white skull on chest and backpack), but definitely don't spray him with matt varnish (you could apply matt varnish with a brush to the joints, etc afterwards).
I'd leave the cabling and rivets in red. Personal choice though. In the end you've made a pretty good effort after such a long break - it's like riding a bike!