The basic problem is there are a lot of different inks. Hair spray will work on some, but not on others. Same with isopropyl alcohol or any solvent for that matter.
The basic challenge is to try to get the ink to come off without spreading it. That means minimum solvent or cleaner and as much blotting as you can. Once the bulk is gone then you can try come scrubbing.
The second issue is to use as mild a solvent or cleaner as possible so as not to do damage to the vinyl. Both hair spray (the cheap, old fashioned flammable kind) and WD-40 can be pretty aggressive. I would probably start with a water-based cleaner approved for vinyl - one I like is Serious Marine Cleaner from Yacht Brite. Whatever you use test a small area with something like a Q-tip fist - don't flood the vinyl. Also put Lava soap - the liquid pump kind - on the list for scrubbing. If there is any residual staining after trying everything you might try a liquid peroxide bleach, like Clorox II. Put it on the stained area and let it sit for a good while, then remove with a wet rag or sponge.
After it's all done follow-up with a good vinyl cleaner/dressing. I like the 3M product.
