Preparing the wax. I have found it best to make up my own "cocktail". Yellow beeswax by itself will certainly waterproof the hemp sufficiently, but is not "soft and sticky" enough to ensure a good seal in the stitch-holes and also to hold together the frayed-out edges of the individual strands of hemp throughout the stitching process. (more of that later..)
Make up a block of softer wax by melting together one measure of yellow beeswax and two measures of black thermowax. Pour the molten mix into rolls of greaseproof paper that have been securely sealed at one end with masking tape. Once the wax has cooled, the paper can be peeled away a little at a time as you use it.
Preparing the hemp. What you are aiming to make up here is a length of twine 16 feet long, made from 8 strands of yellow unwaxed hemp that will taper down to a quarter of its diameter where it meets the needles at either end so that when you are stitching, the awl and the needle are only about half the diameter of the main twine which is following. This ensures that the leather is stretched and the stitch-hole securely sealed. At either end the last 2 feet is gradually tapered down from 8 strands to 2 strands. Start 2 feet from each end and fray out one strand every three inches until there is only 2 strands left. Don't just cut it or snap it. Rub your fingernail over a one-inch length until it parts naturally. That will leave you with about 6" of twine only two strands thick.
Waxing the hemp. This is probably the trickiest bit to get right. You want to wax the hemp thoroughly so that the frayed-out edges of each strand become embedded in the wax and will not start coming apart during the stitching process.
Start from the middle and work out towards each end, working on a length of about 2 or 3 feet at a time. Rub the stick of wax along the 8-stranded twine back and forth several times rapidly until the wax heats up and melts into the twine. When it is thoroughly and heavily waxed, twist the twine to strengthen it and then use a soft cloth to rub the wax further in and also to burnish the surface to a smooth finish. - The smoother the finish, the less likelihood there is of a strand coming adrift during the stitching. When you come to the final 2 feet at each end where the hemp is frayed out, apply the wax in one direction only - toward the thin end of the twine. Twist and burnish most thoroughly here, making sure that all the frayed ends are well embedded in the wax. It can be VERY frustrating when you're half-way through stitching a bag and one or two strands start to come away. So make VERY sure you wax up the frayed-out section of the twine as heavily as possible to thoroughly embed the ends of each strand into the wax.
What you should have now is a length of twine that tapers smoothly at both ends with no stray bits of hemp sticking out. Thread a needle onto the first two or three inches at each end and twist up the two inches of hemp below the needle so that it can not come off.
Adding a loop. Fold the twine in half and tie a loop of about one inch in the centre of the twine. (This is to enable you to hang the bag up for draining after seasoning.)