I do not think aluminum is the best mold media for resin baits, but I have made a few. One is currently listed on the CNC Molds N Stuff website. The advantage to aluminum over silicone is that the shape is very consistent. The disadvantage is that the resins used for casting cranks baits stick to aluminum and hold quite firmly. Once fully cured they are very very difficult to remove, even by chemical methods.
If you use an aluminum mold for casting liquid resin please use a urethane mold release on the mold. I suggest spray the cavity, inside surfaces AND outside surfaces. While the cavity and inside surfaces will allow you to demold your part, over flow, splashing, splatters and other amounts of resin that contact the external surfaces will become permanent if a mold release is not used on them.