If it s just surface rust the most effective removal process is simply using a grinder with a wire wheel to clean up the old sheetmetal.
Rust removal floor pan.
Curiously replacing the full floor pan is actually less work than doing two partial panels.
If you replace left and right side partial panels and leave the original tunnel intact you re welding about ten more feet of sheet metal versus replacing the whole floor.
The front where the pedals are the middle under and behind the front seats then the section under the rear seats.
Take a sponge with a scrubber and scrub at all of the rust spots using the heavy duty scrubbing side.
To scrape off the rust cover the bottom of the pan with a thin layer of salt and scrub it in using a brown paper bag until the rust is lifted off.
The baking soda will help wick up and remove rust that is in the pan.
Patch panel rust repair full floor pan vs partial floor pan.
The floor pan is such a large area i had to tackle it in three sections.
To remove the old grease and waxoyl i have used bits of the old carpet and cut into rectangles sort of five by seven inches or so.
Then make sure you properly seal the floor pans.