There’s no repeatable or universal method for exploiting the imagination. It comes when it comes. It’s maddening.
Generally, the creative cycle has two parts: to take in new or existing knowledge and then let our minds do associative magic.
Breaking monotony, or finding refuge in routine. Whatever you do, it’s all a test of fitting habits into form. Though, I suspect more than half the time you think something works…it’s likely a placebo, which is good enough and the best you can hope for.