Define the problem in your head, as best you can, then just chew on it for a few days. Never let it rest. Keep it perking at some low level of your mind. Keep a pad and a pen in your pocket.
Your brain is the ultimate tool. You carry it everywhere. You can use it while you do other things. You can use it when you may not even be aware you’re using it. But first, you have to make your mind understand the problem you want it to solve. Inform your brain of what need, then give it a few days to deliver.