During the first month after the onset of my tinnitus, I assumed that I can continue doing all of the things that were ok to do before I hurt my ears. That included going for car rides and being in the car when a car door was slammed shut. Eventually I realized that these things felt uncomfortable. I would make sure to wear hearing protection in the car. For the first year and a half all of my drives were under 15 minutes long. Then after a year and a half I went on a road trip that involved me driving for 5-8 hours a day for about two weeks. I learned that my noise cancelling headphones were great at dealing with the noise on a highway. But some people say that they got tinnitus after using noise cancelling headphones, so I made sure to wear earplugs underneath the headphones to protect me from the headphones.
All of this was a long time ago, and I can't remember whether I was concerned about the occlusion effect. It certainly wasn't a problem when I wore noise cancelling headphones. I know that at first I would wear the goofy Peltor X5A muffs whenever I drove. I am pretty sure that I had been wearing earplugs underneath them, but I can't be 100% sure. I think my reasoning for wearing the Peltor muffs was to maximize protection (and add an additional 5 dB of protection). I know that I didn't feel great about wearing them and have the other drivers and pedestrians think that I was a freak. Eventually I began wearing earplugs when I drove and these days I don't wear anything.
If you are getting spikes after driving while wearing earplugs, perhaps your injury is still too raw to handle driving. In that case you might attempt to minimize the time you spend in a car. If you are getting spikes after driving without any hearing protection, then see what happens when you wear protection. It seems to me that the occlusion effect is only relevant when one is at the dentist's. Otherwise, earplugs (good ones like 3M foam 1100 plugs) Are effective, in spite of the occlusion effect.
If I were you, I would "play it by ear" - experiment and then minimize the activities that cause spikes, keeping in mind that eventually you ought to heal enabling you to return to those activities.