In general, most approaches to flare shelters start with finding the 'thickest' part of the vehicle on one side of the shelter. This is usually the base where the engines might be, and often where the fuel tanks might be.
Regardless of fuel type (LOX/LH2, hypergolics, LOX/RP1, LOX/CH4) a few feet of them, as any fuel tank would have is better than nothing.
Lockheed Martin is spending a lot of time and effort in the Orion design on placement of equipment, storage, tankage, etc so as to maximize their value in radiation mitigation. I listened to a podcast with an engineer from there, but do not recall the source, where they discussed some custom software they had spent a long time developing that helps optimize for this aspect.
Thus the goal is first, place as much mass/density between humans and the radiation. Use what you have in hand, then add what can be added/moved as needed.
Any mission will have fuel and water and food. At least some amount. Each has differing amount of value in terms radiation shielding but with planning all can and should be used as best they can.