i think the guy who mentionned using a pound of pressure was making a rough estimate that was way out if i remember rightly (someone feel free to correct me if im wrong, it sounds way too much anyway).
a good way i heard of getting used to tension is to take the key to your practise lock (assuming you have one), put the arm of the tension wrench through the hole in the key and turn the key with the tension wrench, that gives you an idea of how little pressure it takes to turn the key. i found that tip really helpful but cant remember where i read it now

my memory is terrible... and its getting worse!
remember padlocks have springloaded keyways whereas most deadlocks dont, so the pressure you will need will be different (it will vary from lock to lock anyway, but this is probably the major one). just remember to use only enough tension to turn the plug, if you're bending your wrench, thats way too much pressure! (if you're working on an old lock, try and make sure the plug hasnt seized if its difficult to move, it should move a tiny bit even if you are just using a tension wrench and dont have the key!)
as for the tension wrenches with the weights, they're mostly for picking with one hand as far as i remember (i only saw them a while ago when talking with someone with only one useable hand), from what i remember they're more expensive than normal wrenches, so its probably best to stick to normal ones, it helps to be able to vary the tension used anyway. using your hand to control tension also means that you get much more feeling of what is happening inside the lock, as you pick the binding pins, the plug makes tiny movements, if you were to use only one hand and a weighted wrench, you would miss out on 1/2 of what the lock is telling you about whats going on inside
i hope that helps a bit and doesnt just confuse you more (it is 3am so forgive me if its not totally understandable!)
~ Master in Training ~