If you just paint a mask on a layer than it won't work, no, because then it's just a layer and not a mask. If you want to copy your mask across all maps, you have to make sure that your mask is actually applied as a layer mask on whatever layer you want to use. Also make sure to have the layer mask, not the layer selected…
That seems like an awful lot of work for something you can accomplish by simply painting mask edits (or a 100% handmade mask) above the layer that says "Add anything above this layer" when you have the dynamask open. Since it's part of dynamask it gets copied to all maps automatically when you hit Done and it doesn't get…