Jules, Yeah, I loved weathering the Panther to death! First time using pastels to that extent, and worked well I think.
As for the cramp, mine goes from the thumb to the index finger, and also includes the middle finger[:0]
The worst case yet was when I was laying the Tamiya smoke on my 109.
I know why it happens, the AB is too thin for my stumpy fingers, so it takes alot of effort to hold it level and with control.
I was thinking of trying, and still might, of getting some liquid latex, wrapping the brush in some glad wrap, putting a glove on my hand, and using the latex pour it on to make some form of soft handle that conforms to my fingers etc, and also matches the silhouette of the AB.
Or I could get a chunk of wood and sand and file it till it's right.
But that would take up valuable modelling time!