Working with mental ray proxies can be very tedious. As they are used for vegetation alot, the need for variation is there, to makeit look believable. This script gives you options to vary scale and all animations aspects of all selected mr proxies. It also has a minimzed version where you can quickly change the viewport resolution of your proxies, helping to speed up the viewport alot.
If you use this script, be awesome and donate a few bucks!