Test rig power supply question

[catfud]

I've been considering building multiple independent switchable circuits in a test rig, some to run concurrently, and I want to see whether I could run them all off the same +9v supply. Thinking of, for example, a sound generator, a headphone amp, a voltage inverter, and a charge pump all in the same box with various switches and pots to switch between them, and in some cases control their currently active parameters.

Two questions about this:

1. Is this practical from a power POV?

2. If it is, I imagine I would need to be sure that the current draw would be within the capabilities of the power supply, so how would I go about measuring the current draw of each circuit (with my multimeter)?

[catfud]

I found the answer for how to measure the current draw at http://www.diystompboxes.com/cnews/FAQ.html (in case anyone else was wondering the same)