You have to modify your 'technique' somewhat but, essentially, it's no different shooting long lenses with NEX than with a DSLR......
For non tripod shots I prefer to sit on the ground with one knee raised and rest the left hand holding th lens on that knee.
This with Tokina 100 to 300 @ 300,...I also use Canon 70 to 210 f4
NEX-3
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0mm
f/1.0
1/320s
ISO 800