Fiberglass rust repair

Hi all. Getting ready to do some "lipstick on a pig" to my GMC work van. Rear rockers are rotted out and the rockers under the doors are in rough shape too. Plan is to cut/grind/wire brush as much rust away as possible, but there will still be a few spots that'll be tough to get to.  Rust converter to those area's (?), and then glass cloth and resin to reshape and cover the holes, and some bondo to smooth it out a bit. Planning on black rocker guard below the lower body line for the inevitable future touchups. 

I bought some Rust Stop rattle can converter. Hearing mixed opinions on it's use. Some folks saying it doesn't dry completely and glass won't stick to it.  

Would love to get some first hand insight from experienced rust medics here. I realize metal patches/panels are the "right" way, but I need to do this quickly and cheaply and in my driveway. It doesn't need to look perfect and only has to last me a year or 2.  Any advise on how to tackle this would be much appreciated. 

Will snap some pics after coffee. 

In reply to MX_Brad :

I remember dad doing this to his 78 Dodge van, but I don't recall how long it was before he traded it in. It looked fine to my young eyes. 

Here's current pics of the glorious beast. I started picking at the scab to see how bad it is. 

Grind it all down, fill the cavities with spray foam, skimcoat bondo, sand, prime, paint.  Way easier.  

At this point the air compressor and tools are coming out. Once I grind off the majority of the rust, should I be priming the bare metal before applying glass cloth, or resin/cloth straight over the bare metal? Thinking the resin has a better chance of sticking to bare metal. And what about the remaining rust that I can't get at.....rust converter, then glass? 

In reply to 93gsxturbo :

Won't spray foam hold moisture? 

How many years do you hope to get out of this fix .

as they say "rust never sleeps". And it's probably farther than you think , 

I would check all the suspension mounting areas first , 

Then just make it look decent , 

Do you have state inspections where you live ?

Good luck

Don't use spray foam. It'll only hold water and make future rust worse. 

I did the floors in my Beetle. We wire brushed, rustoleumed and then laid in this magical product that is woven roving with matt on one side. Held up great for 2 years until I sold the car. Only problem is that I sealed up all the holes and water couldn't get out!

GAH!!!! Do not fill with foam! It makes it so much worst. It will turn a little bit of rust into a E36 M3load of rust. 

Cut out anything that's too far gone. 

Rust converter on the surface rust. The POR-15 stuff is good but the Rustoleum is OK if you go in multiple thin layers.

Grind the surroundings of the holes to bare metal and epoxy new sheet metal in place. Bondo to blend it all in.

If you do this properly, it won't show and will actually be pretty long lasting.

Edit: You have to make a little flange inside the rust hole so that your patch panel will come flush with the rest of the panel to make it look good.

Went and talked to a buddy who owns a body shop. He basically convinced me to not spend too much energy or money on a temporary repair. "Grind out as much rot as practical, bare metal for the glass to stick to, kitty hair over top, etch primer and rocker guard over that" to paraphrase.  Doing a section at a time so I don't get rained out mid repair. This should be fine to get me a year or 2 more out of the old girl.