Here's step by step how I've painted industrial bases from Necromunda set Plalanite Subjugator Patrol.
After cleaning, washing and priming I've painted bases with old Citadel metallic paint Boltgun Metal. I think that any standard metallic paint will do (e.g. Vallejo Steel).
After that I gave them generous amount of dark wash. Nuln Oil in this case, but again, any will do.
This is my magic "secret" when I paint rust. Rust Set from Secret Weapon (USA) is amazing product.
I've started with darkest and finished with lightest. I was applying it with sponge.
Then I started to work on hazard stripes. Firstly, I painted yellow base.
Next thing was to mask parts that I wanted to remain yellow. I've used 2mm Ammo by Mig masking tape.
After painting black, I've removed masking tape and I've applied some yellow with sponge on black parts and some Boltgun Metal on all hazard stripes.
Finally, I did some more washing and weathering as explained above. I've painted sides of bases in black and I gave nice coat of varnish to all 6 bases. And here is final result: