I wash new jars and lids just because of the odor of the spray that they add, and to clean the outside, and I keep spare lids on-hand. Never want to get stuck with a jar of VAs that needs a lid and the only thing you have on hand is a stinky latakia lid.
Personally, using the 8oz ball/kerr regular-mouth or widemouth canning jars, I usually need one of those for a 1.5 to 2 oz tin of uncompressed tobacco, and it's usually nearly full, or totally full and needs some compressing. A 1.75oz tin of Blackhouse overflowed it even after some compression, so some stayed in the tin. Blackhouse has higher tobacco volume than most, but even some of my wetter tobaccos that weigh in at 1.75oz seem to nearly fill up those 8 oz'ers. 2oz tins of moderately moist shag-cut are the same thing. I want to get some 4oz jars so I can split a fresh tin up and keep the second jar unopened until the first one is done, thereby preserving the freshness of the second half of the tin. Just surprised to see people saying that they are getting full tins into a 4oz jar. Real wet flakes I could see maybe, but I don't know about a tin of Blackhouse or something similar, unless you really press it down a lot, which I don't like to do, so maybe that is the difference.