Since this is being used as a guide, it might be worth being pedantic and pointing out that it's the 'wrong' way of doing it. It definitely beats carrying cash but it's a 'second class citizen'-ish way of using mobile payment.

The mechanism the OP used is the 'pocket change' system which, like its name suggest, can't be used everywhere. It's great for getting casual consummables, getting ice cream etc but doesn't work for services that requires more trust (since there is no credit system and they can't hold a charge on your credit card). For those (like rentals), you still need a local bank account.

Luckily, as others pointed out, it's fairly trivial to open a bank account with a foreign passport. The primary use method is also not to move money from your bank to your WeChat and then use it. People just leave their money in the bank draw from that via WeChat or AliPay directly.

As a random fun fact, you also don't need a local phone number to have a fully functional WeChat/AliPay account with bank linked. Though you do need a local phone number to open a bank account so it's a bit moot.