I was just wondering... When y'all jar up a big batch of bulk tobacco, how do you store it in Mason Jars.  Do you just jar it and put the lid on, or do you seal the jars before cellaring?

If the mason jars are BRAND NEW they are sterelized at the factory. Place tobacco in jars leaving a 1/4 inch gap at the top if possible, wipe the glass rim with a clean dry cloth to remove any
tobacco bits, screw on lid finger tight + a little extra (overtightening could cause the seal to fail) place in a cool dry place (preferably away from a light source) and let er sit for a week. After a week push down
tops to check for a seal. If the tops repedily click when pressed, give the ring a little snugging and recheck after another week. This system has worked for me for 15+ years and I have never had mold of dried out tobacco.

I don't have enough pipe tobacco to worry about storing.

I did see a video on YouTube with a guy using mason jars and then before storing away he poured hot wax over the lids. Not sure if that helps or not, but I guess it's another method.

I just use Mason jars that are clean, new or used. I've had some bulks in store in the same jar for about a year and they still taste just as fresh.
If it's an English, you can even get away with using a cork-lidded jar, but that's if you like letting your Englishes dry a bit, which I do.

Usually I just light them up and hope for the best...... Just being smart ass.

I think the hot wax is a bit overkill, a good sealing jar is more than good.