If you can't blow air through the boiler you know it is clogged. A bicycle pump with a Presta valve has about the right size, although it will lot lock on. You should also be able to blow air through with your mouth. Beware if the boiler is still hot.

Be sure to wear gloves to protect your skin and safety glasses to protect your eyes. Descaling may not be easy.

Attach a piece of hose or a straw and try to pour in a little bit of descaler. Gaffer tape could be useful. I have used heat shrink tube.

Maybe you need to poke out air bubbles with some wire. Maybe you need to apply descaler from both ends.

Warm descaler may work faster. Notice descaler is aggressive, and warm descaler even more so.

The first time I did this repair I let the descaler work over night.

If you manage to get the boiler descaled and to get water through it, you can assemble the machine again. And do a standard descaling.

You may also find a replacement boiler online.