Thats why they make pbw, soak it in hot water overnight,scrub it with a carboy brush also. Rinse/flush well. Do it again if it makes ya feel better. I like to put mine on its side on a towel,capit with some(i use neutral natural dish soap/baking soda cleaner 1/2 full inside and rock it/useing the carboy brush,just for basic cleaning after primary.
Just the hot water and pbw should just do it really.Its suppose to dissolve junk where we cant get to it.