I'm using the Eastwood rust converter liquid quart and their spray for the hard to reach areas. I used a long metal handle brush to coat the inside of my cowl (surface rust only) through the tines, worked well, looks sealed up. I use a foam brush for open areas and brush it on like you would a lacquer, smooth even strokes w/o clumping.
The liquid seems to work better than the spray of course, more consistant and turns the rust black. I just did my interior firewall and under dash, one coat -let dry 1 hour- then a second coat- let cure 48 hrs.
Eastwood Rust Converter
I'll post a pic when I'm home. I haven't used the encapsulator as I plan to primer then paint anyway, I may have if I was doing the frame or other area that would be exposed to water often just for piece of mind/extra layer.
Jon
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'67 Coupe 289 C4, Candyapple red w/red deluxe int., PS, ext. decor group, light group, foxbody seats.
Next to install> stroked 333, AOD, 9" w/3.50:1, PDB.
'09 Black Warriors In Pink with glass roof - the wifes Mustang.
"If it ain't broke, I haven't fixed it yet" -Jon