Your Agent needs your help
Take potential buyers to see your property - this is a BIG job
In the UK the buyer normally knows the local market is capable of driving themselves to see a property. However, non-Spanish property buyers normally have no understanding of the local market. In most cases, they would really prefer not to drive at all. Therefore, your agent not only has to show your property they also need to be a Tour guide and a Chauffeur. The agent will often spend ALL day with a potential buyer. This is where your agent earns their commission.
Assist the buyer through maze of Spanish administration
Once again, because the buying process is SO different to the UK your agent must hand-hold the buyer through the mine-field of Spanish Bureaucracy. This takes time - time that your agent invests in selling your property for you.
Advertise your property on the Internet and help your Agent
Unless you live local to your property you need your agent to show the property and deal with the Spanish Bureaucracy. However, you could really help your agent (and yourself) by advertising your property directly.