I read a while back when I was trying to re-season a pan that you shouldn't use vegetable oil to season it as it goes rancid and gets sticky.
And at the time, that's what I was trying and it was in fact sticky.
So I would agree with that and use lard or Crisco instead.
Veggie oil, lard, crisco, it's all pretty much the same. If you have a sticky, rancid pan, then you a) used too much oil and b) you didn't get the oil hot enough.
The process of seasoning burns off most of the veggie oil/lard/crisco leaving only the hard carbon molecules behind. This is the hard black smooth non-stick surface you're looking for. Carbon can't go rancid like unburned oil.
You'll have to clean that sticky mess off the pan, use electrolysis, oven cleaner, lye, mechanical (sanding, flap paper etc.). Whatever you do, don't listen to the "throw it in a hot fire" types; note how they never tell you about the very real danger of permanently warping or worse, cracking your cast iron.
Then use very light and thin coats of your favorite oil/lard/crisco/whatever on slightly warm and dry cast iron, then heat it up in the oven to over 375 or so with the pan upside down so any oil doesn't collect on the surface. When I season or reseason my cast iron, I usually will take it up, in stages, to around 450-475 degrees or so. As I said, use very light and thin coats of oil; the surface of the CI should look almost dry.
Good luck.