Cassie is exactly the same when she see's the harness she knows she's going out and she goes bonkers with excitement its a bit of a wriggle getting her in but we try to be firm and have no messing, we have one from pets at home that you put her two front paws into then it clips up round her back, dunno if it came this way or my other half fastened it like that to make it easier. Once its on shes fine (well apart from the 'hurry up and let me out' barks, when she knows she's going out nothing like treats will distract her so sooner she realises she has to sit and be good and get it on the better, we have tried ignoring her and going and sitting down if she messes about but we always give it - our fault really must be more persistant!