Set the lawnmower to its highest setting.
Start the lawnmower and allow it to warm up.
Open the throttle to a high setting.
Push the lawnmower slowly through the weeds, starting around the perimeter and working your way in. Extremely thick weeds can cause the lawnmower to stall, so if it begins to stall, tilt the lawnmower back so the front edge is in the air and pull it out of the weeds. Lower it back to the ground gently and push it back into the weeds, going slower than before.
Reset the mower to your normal cutting height and cut again. Waiting a few days between cuttings is better for you lawn.
Start the string trimmer and allow it to warm up.
Tap the head of the string trimmer against the ground to extend the line so you get maximum cutting ability.
Place the head of the string trimmer against the edge of the weeds about an inch off the ground to begin cutting them.
Cut through the weeds along the perimeter and push in towards the back of the section you are cutting.