In my world "snug" is more than "Finger tight" and less than "Tight".
Now I don't mean to be a smart ass, it is just a matter of feel.

If you had the trans out of the car you probably would roll over the front drum and tighten the band until it dragged or even would not roll anymore, then back off the 2 or 3 turns on the adjusting screw and tighten the locknut. And do the same on the rear band. Make sure the filter screen is clean and that the fluid is up to proper level cause you may just be lacking fluid.