I hesitated to post, because my steam time is all Scotch marine boiler all manual firing and it has been pointed out that it is obsolete. But on an exam, I don't really remember them specifying what type of boiler you had to talk about.
We always bottom blew the boiler down to empty it when maintenance was due. The boiler was first isolated from the steam range, and the fires pulled. The pressure was allowed to drop to 100 psi before we blew it down. The air vent was opened. Then after the boiler cooled, you could open the manhole doors.
If the boiler was on a long term shutdown, it was water wedged. To put it into service it was pumped it down to working level with the GS pump then fired. As BP said, it was with the smallest burner tip, 1 minute firing, 10 minute soak. What this does is set up of thermal circulation in the boiler to prevent localized hot sports which could lead to furnace collapse. When the pressure starts to come up, the firing is increased to 3 minutes every 10. ( When you hit 100psi, it was time to get the steam pumps running on steam instead of air, if you run out of steam, you started all over on air-happy daze
If you had to dump the steam pressure in a hurry, the boiler was isolated and the pressure relief valves "eased" allowing the steam to vent to atmosphere. In 4 years I only saw it done twice, one to repair a leaking gasket on the main steam stop flange to the boiler top (that was fun) and another time to repair the gasket on the main feed valve.
For a drying agent we used barbecue charcoal.