In this story I decribe my own way of proceeding.
I explicitly do not recommend anyone to do the same.

There are:
  • hazardous voltages
  • dangerous currents (may cause serious burns with shorts)
  • possibly exploding capacitors
  • other risks yet unknown
when working on power supplies!

If you still decide to follow my way, keep in mind:

You have been warned:
The author does not take any responsibilties whatever for health damage or economic loss or damage.
You do everything at your own risk!
Professional equipment
Professional equipment makes working easier and much more safe. I use special clips to get access to those parts of the circuitry that don't have plugs or other easy accessible points:

clips

The upper one has got a flexible leg and little "claws":

clip_claws

the lower one is rigid and has got a small hook.
clip_hook
Both are very well insulated and rated for a maximum of 1000V.