Hi. I hope the original poster doesn't mind me butting in, but as far as pressure sensitivity in other apps goes, I have to say that Autodesk Sketchbook is hard to beat. It is responsive and quick and you can easily draw the faintest of lines. You can build up a stronger line with repeated strokes or more pressure - just like the real thing. It is noticablty better and more natural feeling than all the other Android drawing apps and would certainly make a good benchmark.
Just wanted to add - the drawing and pressure sensitivity in Flipaclip on my Galaxy Note 10.1 is already pretty good.
A toggle-able overlay sounds like the perfect solution. Would be great if the transparency could be adjustable. I've sent you some grids that I use.
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