A list of missions or something? I have some of his papers, but I'm pretty sure they don't mention anything of the sort. I have tens of letters he wrote home to his sister as well, but he generally avoids talking about the war directly, instead opting to discuss the weather, conditions, family and friends.
Luckily for future generations of historians, we live in the age of archives!
I infer from his being a Rat of Tobruk that you are mostly likely an Aussie, and the Australian National Archives and Army have helpful services to help people trace relatives in the war. Archivists tend to like it when people do that, actually.
If you have his papers, that's an excellent start. I would dig through them to see if you can find his enlistment papers. Once you have that, you can find out his unit and dates of service. Once you know his unit and dates of service, you can check the unit histories and war diaries to find out what the unit was doing. For example:
I know that my grandpa, Joe Bloggs, enlisted in the 15th XYZ Dragoons in WWII.
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I know that he was in the HQ company all through the war.
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I know that he was wounded and resting between July and November 1941.
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I go and check the 15th XYZ Dragoons: The Official History and also, if I can track it down, their war diary from the National Archives.
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I can therefore infer, from the Official History and the war diary what the unit was doing, and therefore what my grandpa was doing. In July, the 15th XYZ were fighting in the battle of ABC, and the war diary says that radio operator Bloggs was wounded by artillery fire then.
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And thus can you reconstruct your grandfather's experiences.
It probably won't be that easy, but that's a rough example of how to go about it. Of course, if you find primary documents like personnel rolls or medical rosters, that might simplify things.
Also check the London Gazette - if your grandpa won a award for gallantry, he should be in there, though sometimes people got missed.
Good luck!
Virtually every regiment published a day-by-day account of their activities after the First and Second World Wars. You can probably pick up a used copy for a relatively small amount of money on Abebooks.com. Most of these regimental histories will also include an index by person, i.e. "Smith, Lieutenant John, pp. 4, 6, 9, 10".
Assuming you know your grandfather's regiment, you can call their regimental museum. Some of the regimental museums have been amalgamated and represent several regiments while others will be dedicated to an individual regiment. The historians and archivists working at these institutions love to field requests from people looking to explore more about their past, so do google them and shoot them a call when you find out more.
Good luck!
See if there is a regimental association or similar. I contacted my father's Squadron Association a couple of years ago. Although there were very few survivors, I met them at a lunch. They identified a photo of an attack on a U-boat I had, and I met the widow of one of my father's crew. Also met a DFC winner from another Sdqn that sunk a U-boat.