Remove the drums & flush the brake dust out with brake cleaner; also spray the entire inside of the drums. Once flushed and reassembled, squeak is gone. This lasts for about a week or two, then the squeaking starts again. You must grease the backing plate where the metal frame of the shoes contacts it.
I was able to do this without removing the shoes by putting some white teflon grease on a thin plastic card and slightly prying the shoes away from the backing plate with a screwdriver. There are 4 contact points, top and bottom of each shoe. If Toyota had lubed this properly at the factory, there would be no issue. The noise is created by the brake dust between the rubbing points. A different brake compound may make no noise.
Make sure you don't get any grease on the shoe friction material.
My '92 pickup never squeaked like that, it was really annoying.