Polination in small cactus collection

in July I acquired a mammillaria, currently identified as polythele quadrispina, at a local garden centre. I did
not expect any flowers this year but at the end of August it started producing flower buds and continued until
early December, total of 14 flowers but in sequence. I was unable to establish if this variant is self sterile
but I attempted self pollination. The flower remains remain firmly fixed to the cactus, can anyone say if I may
get any viable seed and how long before results show, are any of the mammillaira self pollinating?
I have a Acanthocalcium glaucum which produced a flower, net search suggested self sterile but I
self pollinated it anyway and this resulted in some seeds and now 18 5mm seedlings.