I would get rust converter and brush/spray it on the metal. It will turn the rust black. Then use a good enamel paint. Plasti dip is not practical
Plastidip: I agree with not using plastidip (IMO on anything), but especially on this.
Rust Converter: I tried Ospho first and it was largely ineffective.
After Ospho
Paint: So then I used RustBullet Automotive 2 coats grey, the 2 coats gloss black,
after sanding and de-greasing the area first.

1. For anything other than on the hitch, it is messy.
2. It was expensive (comparatively).
3. It takes more time to brush on (comparatively).
4. Unless you have a second vehicle for towing it's not going to be a problem you'll ever be able to fix.
I see it as more of a yearly maintenance thing.
If I was not planning on using Rust Bullet on my frame I would sand, degrease, prime and paint with some rust inhibiting Krylon and be done in a weekend.