I started to paint the sub frames after scraping off loose rust, which wasn't much, and paint i then cleaned it with Eastwood's "Pre" worked great, then put on Rust encapsulator.

  These are the sub frames after I sprayed a chassis paint on them.
The sub frame in the back holds the differential and the sub frame in the front holds the transmission.

These are the two products I used on the sub frames, both from Eastwood.com and very good products.
Spread very easy and bonded to existing paint very well.