Does anyone still make some?
I remember looking at a show and some car mag and they used a sprayable filler.

http://cgi.ebay.com/ebaymotors/Evercoat-...4#ht_2603wt_970

Or

http://cgi.ebay.com/ebaymotors/Evercoat-...ve_Tools&ha

And

http://cgi.ebay.com/ebaymotors/Evercoat-...Motors_Automoti

This is probably as close as you can get....
http://yhst-13811118617756.stores.yahoo.net/evfefi.html

I use a product from time to time called "Rust Defender". This stuff will really build fast and it is a two part system which requires a catalyst to set up. You do have to use a larger air cap or fluid tip to get proper sray out but it lays down well. Block sanding is easy and I have nevr had any problems as a substrate. If you don't need that much build up the good old PPG K-36 is about my favorite. It also is a two part product that gives excellent performance. The nice thing about K-36 is the fact that it can be tinted using PPG "Radiance" dye to be used as a sealer coat before final color coats. There are others out there but these have never failed me. Good Luck! JC.

I'm sorry.......but I had to comment on how beautiful the Charger above is

Is that F8 ?

OK back to the question

Glad you enjoyed that photo. Yes that was F8 PPG paint that I used on this complete strip,repair damage and re-paint. This is the nicest R/T charger I have ever had the pleasure of working on. 39,000 rust free miles! I repaired a lot of dents but no rot. The car actually had factory lead repairs to a crashed area down low where the quarter panel and rear valance meet. The lower control arms were still bright bare steel!!! Thanks. JC.

Z-Chrome Rust Defender is a product similar to what you're looking for. It's got an etching compund in it and works great! I've got a couple old school friends that will use nothing else! Check the swapmeets for the best price.