Posted pollen survives reasonably well folded into paper inside a sealed bag, provided it went in dry and stays cool in transit. Viability drops over weeks rather than days, so a slow delivery is not automatically a wasted effort. Methods for drying, packing and checking posted pollen are explained on https://breederregularseeds.com (https://breederregularseeds.com). Cutting it with flour to extend volume is common practice, though it makes judging how much you actually applied harder.