Hello; I clean gravel by putting about a half to a gallon or so in a five gallon bucket. ( The stronger you are the more you can clean at one time.) I use a garden hose with the spray head adjusted to the strongest jet possible. I spray into the gravel untill the water covers the gravel a bit while moving the water jet around to stir up the gravel. While the sediment and dirt is still stirred up, I then use an section of broom handle with a smooth rounded end (or any three or four foot pole with a smooth end that will not cut the inside of the bucket. ) to stir the gravel some more. I quickly pour off the suspended sediment and dirt. The process is repeated untill the gravel is clean enough to suit me. I then dump the clean gravel into a second clean bucket.
You will need two buckets clean enough to use for an aquarium, a garden hose with an adjustable spray nozzel, a short stick, something to scoop gravel with and a strong back.
I have used colanders and strainers of various sizes and materials. They work fine, but seem to take much longer and use a lot more water. Over the years and after most likely cleaning tons of gravel, the method described is the one I have used more than any other.