Talcum powder, talc, is used because it absorbs moisture quite handily. In the garden or compost pile talc may absorb more moisture then might be good for the bacteria that are at work there. The question you need to have answered is "is wet talc as effective as dry?"

Many people, I think mistaking the Black soldier Fly for the Black Soldier Beetle, say these grubs are beneficial. However, since the BSF as an adult does little except mate and produce eggs that become the maggots and these maggots need a pretty moist environment to hatch and grow they arfe an indication that your compost is too wet to properly compost, and a oo wet compost pile will not have the active thermophilic bacteria that actually generate the heat you are looking for.

Only humans do 'composting'. This is a very narrow interpretation of composting and I believe it IS splitting hairs :-). 'Compost' (the noun) is broadly defined as "organic matter that has been decomposed and recycled as a fertilizer and soil amendment" and 'composting' itself (the verb) as "nature's process of recycling decomposed organic materials into a rich soil known as compost. Anything that was once living will decompose. Basically, backyard composting is an acceleration of the same process nature uses. By composting your organic waste you are returning nutrients back into the soil in order for the cycle of life to continue. Finished compost looks like soil–dark brown, crumbly and smells like a forest floor." Does nature 'compost'?

To simply answer your first post, it would be better to add sulfur to warm compost while bacteria is more active. With cold soil or compost, the bacteria is not as active and thus sulfur is not being converted to sulfuric acid as quickly. Since the process takes weeks to several months, you will save yourself some time by adding it to the compost...and when it is warm. Since it is a slow process, this is a proactive way to reduce pH. With regards to the spot where you plan on planting the blueberries, I agree with others' comments on the soil test as current pH alone isn't the only factor in determining how much sulfur to add to the soil. Some sites recommend rates based off of the soil structure (sand, silt loam, clay) but rates of free calcium carbonate in the soil are also part of the equation which will be (should be) included in the calculation by your local extension after you get a soil test to determine if additional sulfur is needed beyond the normal application for the size and soil structure. Here are a few links you may be interested in: http://cesanluisobispo.ucanr.edu/files/152040.pdf https://ohioline.osu.edu/factsheet/agf-507 http://www.clemson.edu/extension/hgic/plants/other/soils/hgic1650.html http://msue.anr.msu.edu/uploads/files/Lowering_Soil_pH_with_Sulfur.pdf https://garden.org/nga/calculators/index.php?type=sulfur Though finished compost alone tends to have a neutral pH this is usually what is reported from conventional compost piles…not those with elemental sulfur added. Adding sulfur will effectively decrease the pH... it is one of the few amendments that you can add to achieve a long term reduction in pH. Plant based amendments that naturally have a lower pH (such as oak leaves) seem to have a short term effect as they return to a neutral pH (similar to compost…since they are composting the ground, as opposed to your compost bin). Sure, compounds in the compost will fight back and may work to bring the soil back to a neutral pH, but not completely back to neutral as it would with the absence of the added sulfur. How much exactly is very hard to say as it all depends on the ratios involved. It's not quite fair to say it will be a futile effort. Further, what's the harm if you overdue the compost and bring it down to a pH of 3? If you're just setting it aside to amend to your soil before planting blueberries, just add less, wait a few weeks and retest your soil. If you need to reduce the site further, you'll have readily available compost to add. It's usually recommended to work on your soil a year in advance of planting blueberry plants so you have time to continue to add compost, test and readjust. Adding more compost is always good for blueberry plants anyway...high amounts of organic matter is good for the roots and has a lot of additional benefits. I’ve seen many people report that their blueberry plants do very well with less than ideal pH but high amounts of organic matter (and proper drainage) than if the pH was ideal but planted in otherwise poor soil. Lastly, remember that the soil is ever changing. If it wasn't where you wanted it from the beginning, it will likely take years to get to a steadier state. It's sort of like exercise, if you don't keep on monitoring your progress and working at it, your efforts can quickly fade. I would recommend testing your pH twice a year at the start (I would just use a garden center test after the initial extension test to save a little money) and maybe reduce to testing annually but only after you see that your pH has remained somewhat steady.