Hi, I sent this reply, I don't know why you didn't see it but here it is again;
1. 'Shaking the trees' means taking action that makes something happen'
2. 'Pulsing the system' I am unsure. Maybe, similar to 'testing the water' which is to have a quick look to get the feel of someone or something before going ahead and plunging in. It could also mean breathing life into something, perhaps acting in a way which stimulates.
3. 'Hair on fire' describes frenetic activity. 'As the deadline approached, the project team were running around as if their hair was on fire.'
4. 'Silver bullet' is used to describe something which provides the answer to a problem at one stroke. 'The new method was the silver bullet that solved the production problem.'