Squadron Green Putty

As with Phil, when I use Squadron putty, which for me is actually quite frequently, I'll thin it. I've been using Testors liquid cement to do this for years, and just brush it on where it is needed. Allow plenty of time to set though before you try sanding.

Any sort of solvent which will dissolve/remove Squadron putty will also melt the plastic that it's sitting on. I believe some people use acteone, which is milder (though not by much) than lacquer thinner but it will still soften styrene.

When using Squadron putty (which is quite infrequently these days) I will mask around the area where I'm going to apply the putty, thin it to a thick cream-like consistency with lacquer thinner or liquid cement and apply it in thin layers with a paintbrush.

you can use a little lacquer thinner, but understand there are potential risks at damaging your model.

When using putty you use it sparingly, applied in several thin layers not one thick one. Apply in thin layers working each until you find you need no more. This minimizes sanding to remove excess putty.

Seems like many novice modelers trowel on their putty only to find they've created themselves a mess and a lot more work.

If you are using putty for seam work you might find this useful....Read The Seams.