When I re-apply TIM to my cards I do it just like a CPU and spread and even thin layer over the whole heat spreader like this:
Heres a good tidbit from the EVGA forums before you go scraping it off:
The stock TIM on the 5xx series is Shin Etsu X23. It's one of the best out there. If you're going to replace it, do not replace it with a dumpy TIM.
I would recommend replacing with Shin Etsu X23 or G751 or IC Diamond. I would no longer recommend using AS5.
You mentioned temps in the 90s but nothing about your fan speed. What are you temps when you set the fan to 100%? That's a better baseline than auto fan.
I've noticed virtually no difference between Shin-Etsu X23, G751, or IC Diamond in terms of reducing GPU temperatures. They all seem to run within 1-2*C of each other. Why? Because they're the best.