OK, I've got a '''solution to Random-Cursor-Jumping''' that's inexpensive and seems to work as well as my best solutions to date, but this is low friction. '''Teflon sheet for heat press transfer.''' I got 3 sheets 16 x 20 for $6.75 on Amazon. (I tried most of the things above, they didn't work for me.)
One layer over my 2017 MacBook Pro 15" oversized over sensitive track pad. I just typed for an hour and not one random cursor jump! (Most recently I had 1/16th inch teflon, but it wouldn't lay flat and was expensive. ''I've been working on this for months. ''Most solutions I've found are are not slick enough for finger gestures, this is. )
It lays flat, attaches with scotch magic tape, thin as a manilla folder. On the less plus side, it's brown, and has a slight texture. '''So yo! my 2017 MacBook Pro now works better than Tim Cook's'''.
It's also called "Teflon baking sheet " so maybe there's some in a kitchen near by.....
Hope this helps. (And I apologize in advance if I've just solved a problem that a software patch fixed last week....