If the scale is so thick, you will get better results by removing the bulk of it mechanically first, leaving much less material for the acid to dissolve.
Bleach everything first to make the job less unsanitary, though this won't remove any scale. Then use various pointed instruments, screwdrivers etc to lever off most of the scale in the largest possible chunks. With a stubby screwdriver or a short awl, you can also get at the deposits around the bend, which may be even thicker than those in the bowl.
Obviously don't hit or stab at it with anything - imagine yourself doing dental hygiene work, only on a larger scale (er, sorry).
Stop when you've got as many large chunks off as possible, but don't bother to scrape the surfaces clean. Scoop or flush the loose pieces away, and then switch to an acid descaler.
And don't let it happen again.