I also used the Rust Encapsulator on my interior...
I loved the product...
Thinned it 2/3 Rust Encapsulator 1/3 laqure thinner (I think) per their tech support...
Sprayed it using a a cheap spray gun...
Results were good...
I'll try to post some pics too.
I highly recommend all of Eastwoods products...everything I have used has been top notch!