if you are still looking for help on your issue. So I'm here and willing to do the task for you.
Hope to hear from you.
I followed those instructions to the letter . . . 3 times!!
They do not work for the theme the site is built on.
So it's not as straightforward as you suggest!!
Also, Shopify make it quite clear that they only support this issue to a limited degree. Which suggest's to me it can get complicated and time consuming which is what I've found out to be.
Even the people who built the theme wont support me with this task!!
So that's why I'm reaching out on here.
I can help. The main reason is that it depends on your current theme. The guide from Shopify is for their default theme, not all. So let me know if you are still looking the help on this.