Q:  During oral sex my partner never finishes the deal which makes it very unsatisfying.  How can I persuade her to wrap things up in a joyful manner?

A:  My question to you – does she know you want “the deal” finished?  When it comes to sexual satisfaction, there is no one correct way to please a man or woman; and, you certainly cannot rely upon your partner’s mind-reading ability to know your individual preferences and desires.  
Open communication with your partner is a must for any sexual act you wish to engage in with pleasure.  If your preference is to be orally stimulated to climax, then talk with her about this.  Let her know what feels good to you and what she could do to enhance your climax through oral stimulation.  Listen carefully to how she responds and reacts to your requests.  
Perhaps, she knows your preferences but doesn’t want to carry out your requests.  If this is the case, then encourage her to explain her reasons.  It could be due to jaw fatigue, in which case you could explore alternative positions or experiment with other forms of stimulation to reduce over-use of her jaw and facial muscles.  Or, she may be averse to you ejaculating into her mouth, in which case you could create some kind of signal to let her know when ejaculation is about to occur so that she may switch to manual stimulation.  The point is – you should never “persuade” someone to do something sexually that they do not want to do. 
Finally, sexual pleasure is not just a one-way deal.  You do not mention any concern over whether or not the sexual encounter is satisfying for her.  It could be that she is not bringing you to climax because, in the past, that meant the session was over and she was left hanging.  Make sure that you are paying the same amount of respect and attention to her preferences and desires as you are expecting in return from her.

Important:  Sexually transmitted diseases such as herpes, genital warts, HIV and gonorrhea can be transmitted via oral-genital contact.  If you are going to engage in oral sex, protect yourself by using a non-lubricated condom.  

Reference: Elliott, L.  & Brantley, C.  (1997).  Sex on Campus.  New York: Random House.