Are you asking about mulching or something else?

In the soil mix, I have to have them in containers due to our alkaline soil.

I have been doing a peat, pine bark, bagged soil mix.

Blueberry does the best with composted pine bark or fir mulch. I would not use hardwood mulch for blueberry plants. Any big box store like Home Depot, Lowes and Walmart garden center sell pine bark mulch and fir mulch most of the time. You can compost them in a month or two by adding water and regular coke (Coca-cola). Coke has plenty of sugar (to feed composting bacteria) and a low pH to compost you mulch in a bag in about a month or two.