These are the posts I use and prefer.......
https://parmakusa.com/product/bigfoot-step-in-post-2/
But this particular brand is not available in most places. Might be at a local farm coop or local run farm and home chain. If not, TSC sells a similar but lower quality posts, as do most farm supply stores. They will work the same, just are not as durable, so may not last as long.
With these posts, the only steel T posts you need to drive are on the corners.
Actually, I'm a big fan of all Parmak stuff, but I'm partial as they are an old school outfit based out of Kansas City (go chiefs).......and I have a long term history using their products.