What I have been told is that 2 flute end mills are what you want for machining aluminum. A light lube like kerosene (many people like WD-40) is perfect for aluminum.
Four flute mills are for steel. You want real cutting oil (like the sulphurized black stuff), applied with a brush on the mill shaft from the ever present tuna or cat food can.
Buy good mills. You can get them sharpened, but the diameter will be reduced and they will never be as sharp as a factory mill.
Carbide mills are tricky and expensive. Best avoided for a guy like me. Unless they are flooded with lube, they should be used dry (uneven lube will cause thermal stress and crack them). They are really for a production environment where they are worked hard and pushed to their limit.
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