It is important to understand that the putting green and infill must stay dry during this filling process.
If the infill or putting green get wet the infill will clumps together, thus not allowing the infill to get between the fibers of the putting green and be properly filled. Fill the drop spreader with the infill and spread it across the top of the green. The weight of the infill will flatten any small bubbles you may have on your green. Do not apply too much infill at any one time without first brushing the infill into the fibers.

A good basic guideline: is to use 50 pounds of infill over an entire 12 X 30 green between brushings.

Always brush against the grain of the infilling procedure.
You must aggressively brush between all infill spreading. This infilling procedure must be repeated until you have filled the green completely full, past the tips of the fibers and you are walking on the infill, so it will take several times.

By over-filling the green, you are ensuring a consistent level of infill across the entire putting green surface. The objective is the keep the fibers standing vertical. Too much infill and not enough brushing will result to buried fibers.

Once the putting green is completely over-filled, brush the excess off the width or cross-grain of the putting green. Again, this will level out the amount of infill across the entire putting green surface and will give 1/16 to 1/32 inch of the putting green fiber exposed.