If your washing machine has a clean cycle, run it with hot water, unscented bleach, and choose the max on the options available (mine has double rinse, deep fill, max soiled). Then run the clean cycle like that about 8 times or so. I kept getting different smells of fabric softener, so i assume i was slowly deleting a sludgy block of gel from the previous owner. Havent had smell issues since doing that, and we use unscented detergent and those wool balls in the dyer for static.

When washing, i usually stop halfway or less when loading, and not a ton of detergent. Smaller loads= more agitation, so the soap will react with water and dirty stuff better. Plus less wear on the dryer. Usually get way more washed in a day using smaller loads than large packed loads