I have an anodized aluminum muzzle brake I have not cleaned for a long time. A few of the ports are probably more than 50% plugged with carbon. It's s extremely difficult to remove.

What is the best way to clean it? Brake cleaner did nothing. I am thinking about purchasing a small ultrasonic jewelry cleaner for $50 but I habe never used one before.

Not saying it's the best way but the only way I clean one that nasty is scrape it away.

Might be the best way. I thought there might be a way to just soften it a bit even. Foaming bore cleaner helped a little. I am afraid CLR would damage it. Maybe soak it in Hoppes 9?

A gunsmith suggested an ultrasonic cleaner.

Very few things carbon up like the muzzle brake of an AK-74 fired with Soviet 7N6 ammo.

I tried everything.... soaking in Hoppe's #9, soaking in Slip 2000 Carbon Killer, ultrasonic cleaner, etc.

Just by accident I found the one thing that really worked and that was Shooter's Choice Copper Cleaner.
It stripped the carbon off in an hour or so.
I'm not sure how it would affect aluminum or whatever the part is coated with but you might try the Shooter's Choice.
Brownell's and Midway seem to be out of stock, but you can find it from other online sources, including direct from Shooter's Choice.  Make sure to get the Copper Cleaner.

Be careful to test whatever you use.  I use a piece of scrap aluminum as a test.
Note that strong soap cleaners like standard Simply Green, Greased Lightning etc will DESTROY aluminum and anodized aluminum finishes and do so fast.

Thanks!

For what it's worth I fired about 6000 rounds through it without cleaning.

CLR bathroom cleaner ?

Might consider Bore-Tech carbon cleaner.