My two cents about Cuck and Bull (this is just my point of view based on my experiences, it may differ for others)
Most men calling themselves BULL online ore don't even understand the real meaning of Cuckold Bull relationship. They are mostly desperate ones for a quick fuck. The right BULL or I prefer to call it the OTHER MAN in a couples love life, has to chosen based on the consent and the preferences of both the husband and wife. Different people have different perspectives, to really enjoy and cherish this relationship, the couple and the other man, should have similar perspectives about this relationship, so choosing the right partner is the Key for a pleasurable experience.
Other thing I find commonly about the so called bills, they feel all the cuckold husbands are submissive and they need to be humliated. That's not true in most of the cases, most of the husbands want a man, who truly appreciates their requirements, respects their needs and be a good understanding friend. The most important aspect of this relationship is Mutual Respect, Trust and Privacy.
One mistake the husbands also make is choose a bull based on his dick pictures. That's a foolish thing to do, dick and sex is an important part of the whole experience, but it's not the important criteria to choose the man. So choose wisely, choose some one who understands your needs and respects you.
My definition of the Other Man would be, he should be a gentleman, well mannered and who respects the couple. He should be smoth charmer, soft spoken gentleman, who can also turn rough and filthy when needed. He should always stay inside the boundaries you mutually set, respect your privacy, and not misuse your situation for any kind of personal gains. He should make love with your lady (with her consent), with love and passion and gives both of you the ultimate pleasure. He should be a good communicator, too.
This is my two cents on cuckold and Bull relationship. My own perspective.