well i use a tumbler an my coins look like new most of the time I'm simi retired an have the time to do the cleaning, an beside it's part of the fun of the hunt,and if they are clean coin star will take about 99 percent of the coins even the zinc pennies, heres what I do,, when I get home with the goodies, i soak them about 4hours in a home made solouition then when i get a bunch of coins I put them in a tumbler for about 4 to ten hours the silver shines an the pennys shin al so then zinc pennies are ruff some times but still shin an the coin star will take them the one's it kicks out i jus put them back in some times 3 or 4 times but out of about 5 dollors worth i may get 5 or 6 it just won't take those i keep any way, also i seperate the copper peennies from the zinc ones zinc started in 1982 some 1982 are still copper you have weigh them copper pennies weight at 3.0 to 3.1 grams an zinc pennies weight 2.5 grams I keep all the coppers pennies i have about 2000 0f them now also wheat pennies go ion another can, you can purchase a 2 barrel tumbler at harbor fright fo about $ 30.00 on sale when I tumbler the coins I use pee gravel 1/8 inch size or aquairm gravel plane type
al so I use tide liquid laundry detergent as it is low sudsing an water an change the soap about twice.
the tumbler from harbor fright has rubber barells they have a tency to turn the coins black, to fix that problem I cut a plactic coffee container to line the tumbler an al so both ends that keeps the coins from turning black in color, and never never!!! mix clad coins with pennies or they turn copper color that gose al so for pre soaking!!
what I found for pre soaking is to mix 1 cup of mr clean with one cup of amoina an 1 cup of water this al so works very well on rings an other julery but remeber to seperate the pennies an silver
as for as the cost an time you won't come out , but in about 6 or seve years you may brake even lol Me i find about $100.00 to $150.00 in coins a year i have about 5 years to brake even, But thats not the point, the point is the fun,,, of the find if you fig all the hours of fun you have doing this its very cheap entertainment, an i mite add that my wife loves to go along on my hunts and we spend a lot of time together,, now thats what it's all about