While researching the Island dungeon puzzles I came across this longplay of the game featuring an interview with one of the developers that you may enjoy :) The dev says the switch puzzles are bit-masking: so some switches re-press others. For the 3 x 5 one, the outside hint seems to be best; go left to right in the top row, then the same on the bottom, then re-press the leftmost switch and the rightmost in that order, as they re-activate each other. For the 2 x 3 one you can get around in nearly one pass: start at the bottom right and go clockwise around (left through the bottom row, right through the top row), then you only have to re-activate the top-left corner. For the one in Mermon's Fortress, start with the second from the left in the bottom row, then the third and fourth. Then hit the bottom-left and continue around through the top row, and loop from the top-right back to the bottom-left for just one re-activate and done.