How to set up WeChat Pay as a tourist without Chinese bank account (since Nov 2019)

For the longest time it was not possible for tourists to use mobile payments in China, because both WeChat Pay and AliPay ⁠— the two dominant mobile payment platforms ⁠that processed $41 trillion USD of payments in 2018 — required having a local Chinese bank account to work
But since November 5, 2019, both apps has simultaneously started to allow foreign users to link international credit cards, without needing a Chinese bank account. This means that tourists can finally pay for things in China without carrying loads of cash (some Chinese businesses have started to refuse cash payments, although the government is discouraging that)
For tourists, AliPay and WeChat Pay work slightly differently:
AliPay requires loading money into your account. Max 2,000RMB ($285USD) at any given time, unused amounts are refunded to your card in 90 days. AliPay also requires you to have a valid Chinese visa
WeChat Pay doesn't require loading any amounts. It works by simply linking your credit card to the app, and that's it. BUT the caveat is I've tried it a couple of times and WeChat Pay seems really finicky. Sometimes the card works and sometimes it fails with no rhyme or reason. For now I don't recommend WeChat Pay — use AliPay instead until WeChat Pay fixes all the bugs
I've written here about how to set up AliPay. Below are the steps to set up WeChat Pay. By the way, I recommend doing this before you go to China, because you need to be able to receive SMS text messages to verify your phone number.

Here's the step-by-step guide on how to set up an WeChat Pay without a Chinese bank account (takes ~10-20 minutes):

Before you get started, make sure you have two things that are required to set up the AliPay account:
A credit card issued by Visa, MasterCard, American Express, JCB, Diners Club, or Discover
A working phone number that can receive SMS text
Download international version of WeChat for Android or iOS. WeChat Pay is not a separate app, but rather a function within the WeChat app itself
Open the app and follow the on-screen instructions to sign up for a WeChat account. You can refer to this WikiHow article on setting this up. WeChat account is tied to your phone number, so you will need to do this somewhere you can receive text message (they will send a verification code to you by SMS text to complete the set up)
Once you have the WeChat app set up, go to the "Me" tab on the bottom right, then click "WeChat Pay" button in this tab to go to the main screen for WeChat Pay
On the main screen for WeChat Pay, click "Wallet"
The first time you do this, you will be asked to set up a 6 digit payment password (all numerical). Enter your password, type it again, and press "Done"
Then you will be taken to this screen showing your wallet information. Click "Cards" then click "Add Bank Card"
Enter your card number (must be Visa, MasterCard, AMEX, Discover, or Diners Club) and click "Next"
Confirm your credit card information is correct, and fill out your billing details associated with the card
If the autofilled card information is not correct, you can click on it and manually change your card type from the list. The cards are all sorted in alphabetical order, and if you scroll down you will find your card
Anyway, once you're done filling out your billing info. Check the "Accept" checkbox and click "Next". WeChat will try to authorize a charge of $0.05USD to make sure the card works. If it does, your card information will be saved
The set up is done. Now when you want to make a payment, you can do so from the "WeChat Pay" screen in the "Me" tab. In this tab, click the "Money" button to load up the payment QR code
The first time you click the "Money" button, you will be asked to enable the payment QR code. I cannot take a screenshot of the screen, but there's a big green "Enable Now" button that you will have to click, at which point you will be asked to enter the 6 digit payment password you had set up earlier to enable the payment QR code
Once you've entered your 6 digit password to enable to payment QR code, it will become permanently visible on the "Money" screen. Now your set up is officially complete!
Note that there are 2 ways to make a payment with WeChat Pay when you're at a store. One is to have the merchant scan your QR code, and the other is for you to scan the merchant's QR code. Either one works depending on how the merchant has set it up on their end. You can see this video to get a sense of how to actually use WeChat Pay at a store (it's for AliPay but WeChat Pay works exactly the same way):