Use the force on all buildings (i think it was mainly all the windows) before you destroy them.
Get in all the veihcles, most of them give a trail of studs when you get in.
Walk round any flowers in the grass and studs should pop out.
The last ones i was missing was some flowers in the N/W corner of the map, i drove round in the tractor and more flowers apeared, i'm not sure if you need to be in the tractor or if you can be on foot.