Yes, you can apply a truck bed liner on top of Rust Bullet. Rust Bullet is a high-performance, industrial-grade protective coating that can serve as an excellent base layer for additional coatings, including truck bed liners.
Apply the minimum two coat application of Rust Bullet and allow it to fully cure, then scuff the surface with 80-100 grit sandpaper to provide a profile and ensure good adhesion of the truck bed liner. Check compatibility to ensure the bed liner is suitable for use with Rust Bullet.