In the beta v629, there's an interesting new feature for the twisted minds out there. You can use a grid as background for other grids. It's handy when you want to use the same power in multiple grids. This way, you can have a primary grid generating your values and then share it. It's a bit the equivalent of sharing the attribute layout but for sources, without the limitation of keeping the same layout.
There's also a new grid.backgroundAt function letting you manipulate the background value with your sources. So you can get the values from another grid and invert it or apply any kind of crazy formula. The shader mode is also pretty handy for this kind of manipulation.
The way it works is that you go in the media manager and add a grid as a media. Then use this media as background for your other grids. Since it's a media, it's also easy to update it and keep track of what are the grids that you are sharing.
Enjoy!