I've never heard of anyone trying osmopriming with daylily seeds, interesting question. They will germinate in a few days at room temperature after a few weeks' of stratification (damp chilling) or during soaking in hydrogen peroxide at around 1:9 household H2O2 to water. Both these methods break seed dormancy. When I did my germination experiments I did not try osmopriming.
Daylily seeds that do not have seed dormancy will germinate quickly if just planted with no pre-treatment at all, but do you know yet whether your daylily seeds typically have seed dormancy? Osmopriming does supposedly work with some kinds of seed dormancy but whether it works with the type of seed dormancy daylilies have I don't know, you should try it (unless the seeds are too precious to risk!) and let us know.
I did test soaking in plain water and it inhibited daylily seed germination, they germinated better just planted in the normal way without pre-soaking. I also tried a weak solution of sodium hypochlorite and the seeds died.
Scarification (removing or abrading the seed coat) also works with daylily seeds even though the seed coat is not impervious to water, but there's more potential for rotting without a protective seed coat.
You should ideally also have enough seeds to start an untreated control group planted at the same time in ordinary seed starting medium, and maybe also a group with stratification. Otherwise you won't know if osmopriming had any advantages over other methods or even over no treatment at all. If you don't have enough seeds to do all this I'll see if I can get enough for a comparison trial. I may also try PEG because that is also used for osmopriming.
