I am in a bit of a quandary , regarding the exterior inspection of a B737-700, that I wanted to ask.
When doing an "external inspection" you are looking for evidence of the leak, not the leak its self. You cound have a leak in the aileron servo the the evidence, puddle of fluid may be many feet away. Fluid runs down hill and the leak in the aileron servo may show up as a puddle under the wheel well.
Even if you pressurized the hydraulic systems it may not help in finding the leak, just make more evidence.