Use privacy preserving coins such as Monero instead of Bitcoin as it is much more safe. Not bulletproof, but much better.
Monero also complicates any type of investigation much more than Bitcoin. It is very hard for investigators. They also don't want to burn techniques unless the case is absolutely massive.
Also make sure to never use an exchange that forces KYC.
As long as one takes moderate measures to stay anonymous on the network level, an exchange that is P2P or doesn't force KYC can be used to convert. There are many of them out there.
You can do it on Kraken just fine. As long as you're ok paying taxes on it (since Kraken is KYC), you're still shielding the source of the funds, which is the primary utility of Monero.
Or to put it another way, it's good for "money laundering", but not "tax evasion".
Of course it's difficult. Even if you could convert it to cash you wouldn't be able to deposit in any bank or meaningfully use it. The moment you do anything with it you'll trigger anti money laundering laws and have to explain where the money came from.
From a criminal perspective you may not have to launder it. Just deposit your XMR/ZEC into an exchange and sell it. If they ask, say you bought it years ago at $10.
It's not actually that tricky - because obtaining Monero anonymously is also tricky, the only way to do so is to put on a pair of rubber gloves, and anonymously send cash from a mailbox that can't be traced to your identity. The other side of that transaction is the party interested in converting to cash. Because there's so much demand on both ends, there are many reputable vendors with a long and trusted history of those transactions.
I also noticed on a darkweb site that keeping monero in an escrow account is used to further muddy the trail. Not sure how effective that actually is though.
Monero also complicates any type of investigation much more than Bitcoin. It is very hard for investigators. They also don't want to burn techniques unless the case is absolutely massive.
Also make sure to never use an exchange that forces KYC.