This looks like a cake build up to me too.
It honestly is not difficult to scrape yourself.
I use a sharp, thin knife.....a Buck Stockman.
I hold the blade edge directly against the bowl side.
In other words, dont use the knife like you would be whittling a stick.
Use it as a scraper.
Then just slowly scrape away the crispy, shiny stuff.
If you do not use too much pressure, you won't hurt the wood.....briar is tough.
Even if you were to gouge the wood a bit, no big deal at all....future cake will fill it in.
Just work at it slowly, it will be fine.
You will know when you hit wood.
Then you can use sandpaper to smooth it all out to bare wood and start your own build up of cake.
Ive done this with dozens of pipes and I started with zero "trainning".
The only time I slightly damaged a pipe was using a Butner pipe reamer.
That was my fault, not the reamers!
Or, skip the knife and just use sandpaper. It will take longer but way less chance of damaging anything.