dragging alphas onto the model offers the option "Selected mask", so I can control where new fills go inside the mask I'm working on

Right now a very common workflow  of mine is to create a masked fill layer to display a certain Visual like let’s say green slime across the entire suit of a ghostbuster.
Once I set up the layer properties I define my mask by using generators, paint, and most importantly fills, because I can reposition or scale them later.
In order to add a fill effect to my mask I drag it from the shelf onto the model, so I get a good starting point for the position. 
At the moment the only way I understand how to do this is to drag an alpha to the model, choose “Mask” from the pop up menu. This creates a new layer with the mask I actually want to be a part of the mask I was currently working on. So I need to scroll to the top of the layer stack, select the new mask, copy the effect, delete the new layer, scroll back down, select the mask I was working on and paste the effect.
This procedure is most painful the first time around after which I will usually duplicate existing mask effects as a starting point.
But all this head ache could be avoided if there was a command to directly drag and drop an alpha not just physically onto the model where I need it, but also hierarchically into the currently selected mask.

Maybe I’m missing the proper way to do it or this workflow goes against what Painter expects me to do instead, but it is a workflow that works really well for me, except for the issues outlined above.