With this, like all things involved in the lifestyle there is no right or wrong, its about each couple setting their own boundaries, sometimes those boundaries may change from time to time. For me if its the first few times with a bull I tend not to kiss them, after a few times and a level of trust has been developed i would find it hard to have a guy balls deep in me pounding my pussy and not kiss him. When a bull becomes a regular and over a period of time there is that transition from bull to lover, at that point I am very intimate with my lovers and kissing is a vital part of that