Use the meter to check continuity, checking to see that the solder joints are conductive (not cold), confirming that the connecting from point A to point B really goes where it’s suppose go. Also, checking that the grounded connects are good to ground and that there are no unintended grounds.
Also, checking to see that component values are correct and that the published voltages around the circuit are correct. Most of the time, new builders with an amp that does not work or preforms poorly think that it must be a bad component or a mistake in the schematic or layout. But, it almost always turns out to be a bad ground, misplaced or missing lead or a weak or bad solder joint.
In terms of safety, you can do all the continuity checking with the amp off and unplugged, so as long as you discharge the caps, you’re totally safe. Some tests, like checking voltages and biasing (not required in the Two Stroke), require that the amp be on so you need to be careful about where you touch. Clipping one meter lead to the chassis (chassis ground) and using one hand only to touch the other meter probe to various points in the circuit will keep you from sending lethal voltages through you. It helps to know where the B+ voltages are in the amp. There is no virtue in holding both meter probes and moving around the circuit with the amp on, if you slip, you get shocked. I use a test lead with alligator clips connected to the meter probe to check areas where I don’t want to risk holding a probe.