Leadbelcher (Base) – Basecoat, I would recommend going thinner and multiple layers particularly with this paint. Leadbelcher (Base) (like most metallics) is super thick and can obscure details if unthinned.
Nuln Oil (Shade) – Wash thick, don’t let run but do let pool. Extra layers of wash can make for nice, dark Irons.
You can also apply a light Agrax Earthshade (Shade) wash after the Nuln Oil (Shade) dries to create dirty metal that looks like its been used extensively. This is good to do for metal that contacts dirt (IE: iron boots.) This can be done out of pot, or 50/50 with Lahmian Medium (Technical). Progress the wash and do fewer layers as you move up.
For glowing effects, try using any of Citadel’s glazes. They’re great for weapons or armor that are supposed to look “enchanted” or power weapons.
For burnt Iron, after the highlight step up Nuln Oil (Shade) washes progressively (gradient them layer by layer) and end with a light Agrax Earthshade (Shade) wash on the darkest edge. Looks amazing on flamethrowers.