Well I was at the hobby shop the other day picking up supplies and I stumbled across their new rack of Tamiya goods. There was some cool stuff on there but what really grabbed my attention was the Tamiya Modelling Putty Basic Type. It was AU$6.99 for a tube so for that price I had to give it a go:
The Tamiya Basic Putty isn't like your greenstuff or Milliput: it's a single part substance with the consistency of toothpaste (the tube it comes in is the same size as a mini toothpaste tube). Don't brush your teeth with it! It's intended for filling small gaps such as along seams on kits, or between laminated sheets for example on a scratchbuild.
You squeeze a bit onto a putty knife or sculpting tool and then quickly wipe the putty over the area you are filling. There will be a bit of a mess left over but once you let it cure (1/2 to 2 hours it seems depending on thickness) you sand it all smooth and you're left with a flawless finish. The instructions are all in Japanese so it's kind of just try it and see.
It seems like the putty has some kind of metal filling as it kind of catches the light. Remember too that being lacquer based it does eat into the styrene slightly so once you apply it there's no going back.
Before using the Tamiya Putty I was using some automotive spot putty (i.e. Bondo, but mine was a generic brand) for the same purpose and honestly it's about the same in terms of performance. Both seem to have about the same curing time. I know it's a stupid way to think but I feel a preference for the Tamiya putty purely because it's intended for modelling. Both types have a pretty strong smell though - if you have smelled lacquer thinner you'll know what I'm talking about!
The Tamiya stuff is cheaper, but it's also a much smaller tube so economy wise the spot putty is better. It'll take you forever to use the tube of Tamiya let alone the spot putty, so I figure that the Tamiya remains better value as there's none going to waste.
Tamiya - 32g - $6.99 - $0.22 per gram
Spot putty - 150g - ~$13 - $0.087 per gram
Yes that is a massive difference, but how long will it take to use 32g of it? A long time, trust me!
When you get adventurous you can also do advanced techniques with the spot putty, like creating a cast iron texture. I'll have to give it a go soon
Conclusion: I give the Tamiya Putty Basic Type two thumbs up. As easy to use as spot putty but with that awesome feeling of using a proper modelling product!