Rusty screw holes: Tap or Solvent?

I am setting up my new (to me) bike for 2 up.

The frame holes where the passenger foot peg mount screws into are super rusty(see picture).

Should I use a tap to clean out the rust, or use a solvent and a brush to kinda scrape out the rust?

https://preview.redd.it/e58a6in5g7391.jpg?width=2268&format=pjpg&auto=webp&s=cc5d50ec8316caf87307f88421e10b9721f495b8