First:
Do not make the mistake that this is purely abut technical knowledge. Of course you have to have the best possible technical knowledge of your, and your competitors products and apllications.
The other thing is your factorys and products standing and suitabillity to the market. This will never stop to alter with the action your factory takes (or do not take).
Besides searching and learning from internet (this forum) also involve and learn from all levels and of all employees in your company. Especially service people and trouble shooters and other 'hands on' people will have things to tell you. Learn from them and ask for permit to trail along and observe at technical service sessions.
Ask your QA-department to tell about failure reports on technical and other basis, what is done to improve, and plans for improvement for the future.
Ask and visit customers, and consultants (which forescribe your products) what they think can be improved from you product, factory and procedures.
Very often you will find other problems than purely technical problems, perhaps problems the factory leadership is not aware of, or have done nothing about. (Correct price-level adapted to market and competitors is a running discussion)
Remember that the information flow to all inside and outside levels is the most important part of your job. Also informing about 'things to be done' if the market share wants to be increased.
Do not forget to check with your bosses what in their opinion is the most important part of your job. (Not all bosses appreciates a service-oriented sales organization, and sees general service as wasted time)
I know what I prefer, and would have had problems with with non-service oriented sales organizations.
Good luck!