My understanding of the original formula for these yellow slickers was the pure natural latex from the rubber tree, heated to make it soft, added with boiled linseed oil and turpentine during the heating. Applied to the fabric while hot/warm and allowed to cool. (I have know idea what the exact formula was!)
Problem is... that this coating always seems to stay rather sticky (to itself), especially during warmer temps.
Boiled linseed oil mixed with turpentine (50-50) and heated, applied to the inside of the fabric will help seal these pulled apart openings in the original coating.
To reduce this stickiness of the original coating I would suggest talcum powder or plane old chalk dust. (if you don't want to sell like a flower)
My best,
Blair