Sorry, I should have been more clear. What I meant to say was that it wouldn't have been worth buying Hertz points at the price they used to sell them for (around $0.20 per point), and likely also not worth transferring frequent flyer or hotel points like SPG to Hertz if it were possible as those points almost always have more value in their native programs relative to Hertz Gold Rewards.

Good point about taking surveys. I'd forgotten about the e-rewards program. While it can be time-consuming to earn points this way, it's certainly an option. More info on this program here.