I see what your getting at now. Yeah- I find doing anything to buckles this size is real tedious and more than a few bits go flying to the floor monster's lair. However, my own way of doing it is with needle nose tweezers- I have a set of Italeri tweezers that curve into fine, thin and points (with a rounded cross-section)- if I have to bend something of this size I tend to grip it between the tweezers and bend it round one of the sides- then apply it to the subject. This is just the way I do it but I know people that use a small piece of blu-tac to anchor a bit of the buckle and then carefully bend it using tweezers. White PVA glue will also hold a piece of etch in place for a while once it dries- it won't hold it permanently but it will hold it enough to gently manipulate it.

If it was me doing that assembly I'd definetly be bending those parts using the needle nose tweezers. I hope this helps you out a bit Matt.