Hilchos Issurei Mizbeiach 7:4

When planting wheat for flour offerings and libations, they would let half a field lie fallow one year and plant the other half. The next year, they would let the part that was planted lie fallow and plant the other half seventy days before Pesach. If the field wasn’t worked, they would plow it twice before planting. The kernels to plant were selected carefully, and then struck with the hands and feet to remove the shells.

Hilchos Issurei Mizbeiach 7:5

All the wheat for flour offerings had to be struck by hand 300 times and by foot 500 times. They would strike the kernels once and walk on them twice, then strike them twice and walk on them three times. In this way, the kernels would be struck by hand three times and by foot five times. This pattern is repeated until they have been struck 300 times by hand and 500 times by foot to remove most of the shells. Reaching out and pulling back the arm was considered one strike in order to be stringent. After this, the flour was ground and thoroughly sifted.