What is your (unamended) soil pH now? It becomes increasingly difficult to acidify soil the higher the pH is to begin with and it will only be a temporary fix. The soil will sooner or later (usually sooner) return to the existing pH...that is it's nature.

The only effective method to home gardeners to lower soil pH is by using agricultural sulfur. And you will need to do so periodically. Epsom salts will do bupkus and table vinegar is too dilute and will dissipate too fast to be effective, although it can be helpful in altering/lowering the pH of irrigation water. And plant parts - like pine needles - will have no appreciable effect. By the time they dry and fall off the tree, they are pretty much pH neutral.

If soil alkalinity is an issue, it is best to grow blueberries or other acid loving plants in containers or raised beds, where the soil media can be customized to their needs.

Every autumn once my BB bushes go dormant I'll sprinkle a 1/2 cup of elemental sulfur pellets around each base and outward to their drip lines. A $10 bag lasts me for several years (3 large 20-YO BB bushes). I also fert these bushes in the early spring with a similar amount of Espoma's acid lovers blend. They have always been very productive.

I have to grow them in containers as there is no way I could make my soil acidic enough by adding anything.

I will add that you should be careful with sulfur. All alkaline soils are not alike. Soils with a lot of calcium carbonates (calcarous soils) are strongly buffered, so you'd need a very large amount of sulfur to deacidify. At least sulfur is not highly toxic. If you can't get your soil tested, I'd inquire at your local extension about the best ways to acidify in your soil. And again, even with containers, if your irrigation water is alkaline, you're spitting into the wind. If your soil is alkaline, and your tap water comes from local lakes, I'm betting it's alkaline as well.

You could apply some sulfur, and see if the pH changes much. But sulfur acidifies when microorganisms digest it, and produce sulfuric acid. That can take weeks or months. That is, the sulfur itself doesn't acidify, and is certainly not a quick fix.

And not a permanent fix, either.

It is far easier to acidify irrigation water than it is to acidify the soil so that should not be a major handicap. It is regularly done in California for acid loving plants.

That's true about acidifying irrigation water. Not hard to do if the water is unbuffered. But it still takes some effort. Sulfuric or nitric acid are generally used, and have some residual fertilizer potential, though those aren't things you get at Home Depot. Hydrochloric acid may also work, and that's a lot easier to get.

I've toyed with the idea of doing container gardening of acid-loving plants with distilled water. In my climate, we get gallons of distilled water every day from our a/c systems in high summer. I don't want to drink the stuff (think Legionaires disease) but it's fine for plants. That's a lot easier than even rainwater collection, especially in high summer, when it doesn't rain much.

I use Espoma Holly Tone.

I have well water and do not water them much. Twice a month I water with vinegar properly diluted in water. I am not sure what my soil is but it is "around" neutral from my test - neutral or 6.5

Holly Tone does not acidify soil. It is simply a fertilizer for plants that need acidic soil.