Clearly, if all of your staff (and yourself) are now highly efficient in terms of their Time Management practices and you still have too much work then you have a resource issue.
Human resource and recruitment are covered in much more detail elsewhere [see ‘The Complete Project Management package’] and [see 'The Complete Project Management plus PRINCE2'].
If you have identified that your staff have gaps in their skills then you will have to train them.
This assumes that the correct persons have been recruited and that they do not lack basic skills and qualifications to do the job in the first place. This would be a more serious situation.