i agree with using a snake--except what would happen if the snake gets
stuck?

i tend to use chemicals

what i have found that sort of works is to run very hot water or even
boiling water tehn i pour celar ammonia down the drain
stopper the drain and leave overnight
seem sto sort of work

sulfuric acid is hell on pipes
lye stuf is not worth the danger

i have tried 2 part cleaners that foamed up a lot but did not really help

hth
peter