I totally agree with all this — I call it “percolating” — taking time to let the idea brew, let it turn into something, without my conscious interference. I find that chores around the house for this are good too; enough mental involvement to keep me from obsessing over my percolating problem, but not too difficult or strenuous. Washing dishes is kind of a zen experience for me (though I do not have the same feelings about doing laundry).