Re: Yucca blooms starting
To my knowledge no one has made or tried making hybrids with Yucca brevifolia. The flowers of Yucca brevifolia are very different from other Yuccas and I don't think, that the species of moth whích is pollinating Yucca brevfolia in habitat pollinate other species of Yuccas either. It might however be possible, since it's possible to cross Agave with Manfreda, so intergenetic hybrids are possible within the Agavaceae.
I do in the best summers get 25-30% success with pollinating Yuccas, and very low succes rate in cold wet summers. If you have access to pollen from any Yucca keep up trying, you might suddenly get lucky. Remember if you live in an area in which there are yucca moths, you need to protect the flowers from being pollinated by them, or the seeds will be plain Yucca seeds, not a first time hybrid with Yucca brevifolia.
I will hold my thumbs for you in the languages I am familiar with: Break a leg, Knæk og bræk, Bryt ett ben, Hals-und Beinbruch, Breek een been, Ни пуха ни перa :-)