Context for this reply: I am not someone that believes in doing that "Darkwing Dad" thing of slathering the entire part in thinned down body filler because I don't want to sand. I use **SPOT** putty for spots. So none of this will be helpful if you're looking for a material to thin and apply over the entire part.
Point of clarification for those that have never used the
Bondo Spot & glazing putty.
It is not body filler. Bondo is a brand and they sell many products. Most commonly used in this context of props and cosplay is their
Spot & glazing Putty that comes in a tube like toothpaste. It is single part (no hardener required) and is about the consistency of stiff cake frosting. It is wonderful stuff and bonds well to sanded parts and dries in about 10 mins. In the States its about US$7/tube everywhere from auto parts stores to WalMart with very little waste since you can apply it directly and in tiny dabs as needed. Here in AU its hard to find and pretty much have to order from out of country. If you can find it on Amazon and have it shipped be aware it comes in various size tubes that look alike. You can get it as small as 4.5 ounces all the way up to 16ounces so don't mistake a medium price on a smaller tube as a good deal.
What kills ya trying to get this ordered in from out of country is shipping. US$75 freight on a $45 purchase that will be boxed smaller than a pair of sneakers. US$20 per tube delivered by the time you add it up.
From what I understand the equivalent to this in the UK is the UPOL brand. But I haven't used that or found it in AU.
This is the last tube in my personal stash. As you can see in my 'filler bin' I've started using putties from the model/RC store. Vallejo for examples makes a liquid-ish plastic putty and Tamiya putty is smooth and thicker.
Most body fillers are two-part (you have to mix a hardener to the base) and you have a limited pot-life time to apply it. Sure its cheaper by quantity but its more wasteful especially in small quantity and hard to get the mix ratio right when you're trying to do a 10:1 with a batch the size of a kidney bean. However - I did recently run across this stuff that when used in thin coats is 1 part (no hardener) so it gives me a little hope that it might be more conducive to armor use. But I have not yet tried it so I can't vouche for it just yet.
Spray putty is a whole 'nother animal to tube/tin putty. As
PlanetAlexander said the SCA brand has been out of production for months or at least no longer available through Supercheap Auto since they switched suppliers. I'm down to a few cans at this point and will have to start looking at other brands soon. But basically its like a very-high-build filler primer. Smooth and even application from a spray can but indiscriminate and will fill grooves so be sure to clean those out before filling them totally. I tend to keep several different primers on hand for different uses. If you do that be sure to test them for compatibility so brand A doesn't make brand B crack and spider web.
