Step 1 – Grinding Off the Rust
The first step is to remove as much loose rust and paint as possible from the rust hole using a scraper or even a flathead screwdriver. If a disk grinder is available, it can be used to get rid of most of the rust. Be careful to not cut any structural metal, such as corners on doors. Removing as much rust as possible and still preserving the bordering structures is vital so there is a base to hold the expanding foam.