This is what works for me. Rake the bed somewhere near to level then use the rake as a 'tamper' whacking it down vertically like a piledriver. After you've done this over the whole bed start raking it again ' but with the rake handle close to vertical and only doing a couple of inches at a time 'wavering' over the bed and shuffling backwards.

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My Majesty made for him a garden anew in order
to present to him vegetables and all beautiful flowers.- Offerings of Thutmose III to Amon-Ra (1500 BCE)