I think you're right; I tried to find out about tincloth years ago, but at the end of the day I reckoned it was just waxed fabric of some variation in weight, etc.,
We know that the cheaper knockoff copies here really, really, really, smell of mouldy paraffin, while the better quality ones smell of paraffin and wax. The wax lasts longer I reckon, and according to Stuart f who used to work restoring/repairing Barbours it's waxy stuff and and iron and hairdrer type thing that does the business
I reckon if you do your own, some of the resin dissolved in oil that I mentioned a few weeks back would add a little robustness to it, and that's one of the components of Greenland wax as well as the original oilcloths for clothing and maps.
cheers,
M
p.s. Mr Fenna, if I can find it in the coup that is my workroom, somewhere I have three metres of tan coloured wax fabric, and you're very welcome to it in barter for a couple of wee leather bags to hold my tinder bundles
I can probably find suitable thread too, and a long brass zip.
M