Apply the second coat of gel medium, alternating the brush direction to ensure an even application. Each alternating layer should be brushed in a perpendicular direction to the previous coat.
Allow the second coat to fully dry again, turning clear, before applying the next coat.
Continue applying thin coats (and allowing for drying) until you have a fairly substantial layer of gel medium. Usually somewhere between 4 and 10 coats is ideal, depending on thickness of each application and desired final thickness.