Toilets, Sinks, Showers, Tubs and Disposals - redoing an oakum and leaded in toilet flange

we removed the closet flange to put in new subfloor and underlayment that was rotten or non-existent... got everything shored up and now we need to put the flange back in place. (twist and set flange is not an option since waste pipe is only 3 5/8" inside diameter, it is threaded on the outside a system that outdates my knowledge) so we bought some oakum and plastic lead but have no idea how to use the oakum and an extensive search online yeilded very little...

Lead and oakum are really old style system. The oakum is a horsehair type or asbestos "rope" that keeps the liquid lead from going into the pipe. It also has an oil in it to make it pack securely. The oakum is wrapped around the pipe and pushed down into the joint leaving about 3/4" space between it and the top of the joint. It is then pounded into the joint with caulking irons (sometimes called corking irons) that resemble curved chisels. This will leave about a 1/2" of space. The melted lead is then poured in and the irons are used to make an airtight seal around the inside and outside edge of the bell on the pipe. Guess you would not need the oakum with plastic lead but wonder if it is code. Plastic has a habit of shrinking and would allow sewer gas to enter the home. It would also allow the toilet to move. Good luck.