@OP Just as other members have suggested, P2P should be your number one choice on the list, and aside from making them your number one means of exchanging Bitcoin to cash, you should also consider recommending some completely anonymous P2P platforms that don't require users' IDs for verification before they can use their service. When IDs for verification are required, the user's identity is no longer private and can be compromised.
Here are two P2P exchanges that I have used and texted:
1.
Hodlhodl No KYC was needed, and I had a smooth buying and selling experience with them.
2.
Agoradesk registration was fast with just a username and email (not compulsory), and I sold Bitcoin using the platform and received a gift card. You can discuss and choose which payment method you need with your dealer. Their charges are also very low; you are allowed to select the amount of fee that will be charged from you when buying BTC; the higher the fee, the slower the speed of receiving.
Depending on the country and the amounts in discussion, these can be a fair option for those keen to stay anonymous, just... they're pricey. The fees are big. Sometimes a bit too big.
A Bitcoin ATM is not completely anonymous; most machines, if not all, require users to type in their mobile number before they can be able to complete their transaction. I don't actually know if they verify if those numbers are completely fake or real. But they are definitely required for verification purposes.