CARL - Yes the Turpenoid is oderless. I like this stuff because it's easy on the enamel paints, being thats what I use. Everywhere I read, people use gloss coats or future before washing and weathering, I prefer to use dull coats to seal with. This Weber Turpenoid (blue can!) does not harm the dull coat or paint as long as you do light coats of wash / weathering at a time and as long as you let the dull coat cure overnight.
The barrel is gunmetal and that is the color it will remain. Was trying to find something to stand out on this build (markings, paint, etc.) but there was not much to choose from. There were some of course but most of the late war STUGS were solid Dunkelgelb or even a solid primer. Many had no markings at all. So doing a gunmetal barrel gave it a little character and is suppose to represent a replacement barrel. Once barrels were replaced it was often left to the crew to paint, if they did.
Have seen boxes both wood and painted. Think have seen more pics with the boxes painted though. Really think it depends on how you want it, no right or wrong way. Imagine they painted them to help protect and preserve the wood. My favorite I've seen done was by PVT MUTT (Tony). He first used oil paints to make the wood effect then carefully masked areas and painted the base color. After he removed the mask it looked like chipped / worn off paint with the wood showing through. It was in the "Marder Madness" that he did this.
ANDY - Your barrel mad!! They are nice to have. Will have to try the Mona Lisa thinner one day. Have seen it in the store just havent picked any up yet. When do we get to see you get started?
ERIC - The glossy effect is from the heavy oil in the paint. Depending on the kind/ brand of paint has some effect on the shininess of the finish. More than anything is the humidity and temp that effects how it cures. If it is still real shinny or sticky you just have to let it dry more. Down here in Texas it normally takes 2-3 days but this last month because its hotter and drier than hell, it dries flat overnight. When I lived up north it could take a week to dry. You have to be careful spraying a sealing coat (dull coat) on until it is dry. Sometimes if not dry can cause different things to happen other times it works fine.
SATCH - Your III is coming along nicely! Have built small sections as you are doing and have made the whole track as Bin has explained. Often find it easier to build the whole track but it does depend on the susspension and fender clearance. I built my tracks in one piece for the STUG. Many times I build the whole track but leave two glue joints, a top section and a bottom section of track. Do this if it makes it easier to fit back onto the susspension.
BRIAN - She's looking really good with the primer on. All the PE really was well done and left no flaws. Nice job 
Like the colors and texture of the base. Looks like a lot of drybrushing.
BILL - The MG ball mount is Sweet! The screens will help tremendously on the rear deck. Look forward for the color. Did you ever say how you were going to paint it?