Here's how I painted mine.
I sandblasted it and then used a tack cloth to remove any traces of dust. A tack cloth is a sticky rag that the dust will stick to. You should be able to get some from any parts house that sells auto paint. After you get all the dust off, take a paint thinner soaked rag and wipe the whole pit down to remove any oils from people's hands. If there's any oil it will cause the paint to bubble up. After the thinner has FULLY evaporated, you can begin painting. If you have the luxury of painting indoors, lightly wet the floor to keep from stirring up any dust. This is how I did mine and the paint job still looks good after three years. This method should work fine for you. Remember, the higher the temperatures and the lower the humidity, the faster the paint will dry. Hope this helps.
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