Hi @sydney1234,
Welcome to the Bunnings Workshop community, it is fantastic to have you with us.
Instead of the products mentioned in that post, I would suggest using this Rust-Oleum 13.3ml White Tub And Tile Touch Up Kit.
This is an epoxy paint product that is essentially a mix of the two mentioned in that post.
Start by unscrewing the screw to remove the grate, then give the rust a scrub with some CLR Ready To Use Calcium Lime Rust Remover and a brush.
Once the rust has been removed, give it a light sand with some 400 Grit Wet And Dry Sandpaper and then flush it with clean water, then allow it to dry.
Mix the two pots together and apply the touch-up paint with a craft brush.
If you're careful, you shouldn't need to, but using some painter's tape to mask off the area can also be worthwhile.
Let me know what you think and if you have any further questions, please don't hesitate to ask.
Jacob
