In reply to kamsy:
I am no expert myself but I wouldn't get weight vests etc. Also 10 seconds are fine, there are different programmes on deadhangs from the little I've read I think you are not supposed to do them for more than 8-9 seconds at a time (obviously you can do sets) but I guess it depends what you are hanging off etc.
I'd be a bit careful with deadhangs - funny as it might sound, it's not too difficult to go wrong with them I think. How long you hang for, how often you do them and even how you are hanging (personally I think it's bad to just hang, you need to maintain a decent amount of body tension and arms should be a bit bent, not straight).
In any case, as mentioned previously - you'll build strength from climbing at first. And 1 hour's worth of bouldering is not insignificant, especially if you are testing yourself.
And lastly, it sounds to me that it's endurance you are lacking the most - not strength!