After you use the kindness elixir on Amoniak's attendants, you can reach a room with a large suit of armor.
Save the King
Have 
Fingus push the loose brick on the tower to be launched up into the tower window.
Click the helmet to open the visor. Then use the crown on the helmet.
Get a Feather
Have Fingus click on the feather on the back of the helmet to get a feather.
Get a Brush
Have Fingus
use the feather on the can next to the painter to get a brush.
Get Another Cockroach
If you don't have a cockroach, go back to the throne room and get a cockroach like you did before.
Have Fingus use the cockroach on the hole in the bottom
part of the screen, then use the brush on it, then use the pepper on it,
then use the kind elixir on it.
Get the Buffoon
Now go to the throne room and you find that Amoniak is gone. Click on the
Buffoon and he will become a character that you can click on. Switch to
Fingus or 
Winkle and
move the cursor to the bottom-left of the screen until it turns into a
door icon, and click to go
to the armor room, or move the mouse to the top of the screen and choose the
wooden sign, then click Armor to go to the
armor room.
Shrink Everyone
Have 
The Buffoon stand to the right of the machine in the left
side of the screen. Then have Fingus stand under the
machine, then have Winkle stand under the machine.
The Buffoon will automatically use the machine to shrink
everyone. You will go to The Desk.