My surface table was brightened up with scotch brite and Wd. Bit of elbo grease and she's a smooth as silk.
Best way to do it is by hand so it stays flat.
A brush grain effect will be far easier to get right with a light glance over using scotch brite rather than a brush. Don't press too hard and keep it all going with the lengths.I'm planning on wire brushing them in order to create a uniform finish.
And yes they are just gates for an industrial unit. If they where for domestic then that would be the way to go.