Personally speaking, I wasn't given the practice in a formal ceremony or anything. My lama basically told me "you should do the black tea each day" and left it up to me to find the prayers for myself, by asking the right students the right questions. When I say 'right', I mean students I already knew had the practice, and questions that showed my guru had given me permission.
I would not have known who to ask had my guru not mentioned Dorje Shugden's practice before. So my experience helps me to answer your next question about requesting for a secret practice. I think sometimes a lama might talk about a practice but not say he or she possesses it. For example, a PhD holder can talk to high school children about physics. The children will understand that this person knows more but they don't know more about what exactly...and if THEY want to know more, they can request.
If we keep the practice to ourselves, it definitely WILL die out when we die out. Therefore I think that the adage does apply...if we spread it, yes of course there is the RISK of the practice dying out because not all practitioners are top notch. BUT amongst the mass of 'poor' practitioners, there will be one or two accomplished people. Without spreading the practice, it may not have ever reached these accomplished people to be kept alive within them. Besides, the 'poor' practitioners will still gain the benefits from the practice, since the object of the practice is an enlightened being.
In any case, I don't think it's for us to judge whether the practice will die or not, because I believe every guru would've thoroughly checked out his or her student before imparting secret practices, and know that it will benefit them in some way.
My 2p!