I thought all paints could be sanded and buffed. I know that base coat/clear coat can be sanded and buffed as long as you do not sand through the clear. I don't intend to do a base/clear for the simple reason that repairs will usually leave you with a halo effect around the repair due to fading of the clear coat. This is why bodyshops won't spot repair a body panel but instead will paint an entire panel.
Why would you stay away from polyurethanes?