I agree, season and use.
I don't know how you removed the rust; I used an electrolytic tank on my skillets. I had one BSR with some very fine pitting on the cooking surface; I seasoned it and just left it upside down in the oven to cool. The next day I warmed up the oven again (gas) and found that when it got warm and I pulled the skillet out to wipe on some more lard that it had flash rusted. So I had to start over.
Here is what I found. Even though I'd e-tanked the skillet, scrubbed with steel wool and vinegar, rinsed repeatedly, and even wiped down with oil before attempting to season, apparently there was still some loose rust and dirt in the pits. Here's what actually worked. Using Jeff Rogers' seasoning method but with lard instead of Crisco, after initial heating and wiping on/off the lard, my wipe off rag was coming away brown. So the hot lard was pulling stuff off the iron that soap/water, cold oil etc. wasn't getting. So if my rag came away dark, I'd wipe on more lard, stick it back in the oven for 10 min. or so @ 200 degrees, rewipe. If it came off dark, do it again. It took 4 rounds of this to get a clean rag. That skillet is now one of my best users, and I restored it only a month or so ago.
Just thought I would pass this on in case it helps anyone else with a similar rusty skillet issue.