Please read and follow the safety rules in the Material Safety Data sheet for all chemicals!
I am a big fan of using car body fillers for these models. They have several advantages over standard lacquer based putties, like Squadron Green Stuff:
They harden much faster, enabling you to accomplish much more within a given period of time
These fillers adhere better and are stronger than plastic putties. This is especially evident when filling edges.
When used in small amounts, the odour is no more objectionable than regular putty.
These products can be used to add mechanical strength to an assembly.
One problem when working with these products is the container size – they were designed for auto body shop applications, and are sold in large containers. You should pick up some extra tubes of hardener when you purchase this product. These can should be kept tightly sealed to avoid drying out. I generally take small containers and transfer some of the product into these for use on my workbench.
I use disposable, wax covered paper plates as mixing palates, putting a small amount of material on, and then, using a toothpick, pick up the amount I need for the task at hand
Mix thoroughly but quickly, as the product starts to harden quickly. Depending on how much hardener you use, it will go off between 45 seconds and several minutes. Practice a bit to get a feel for how much hardener will give you the working time you need; you will soon learn to evaluate the colour intensity of the final mix for working time