The push model, used to manage Computing Grid resources, raises several issues that prevent employing the resources at their full capacity and, thus, limits the Grid throughput. While the push model remains necessary to get access to the resources, this paper aims at addressing some of these issues to make better use of the Worldwide LHC Computing Grid. After a thorough analysis of the DIRAC Workload Management System and its design to assign Pilot-Jobs, we propose different optimizations to improve the submission system and the grid throughput. The obtained results show significant changes in performances and enable the generation of a larger number of Pilot-Jobs to exploit grid resources better.