The problem isn't really about identifying the "hot" coins - but rather the history of the coins - you can transfer the same coins constantly to your own wallet

The problem isn't really about identifying the "hot" coins - but rather the history of the coins - you can transfer the same coins constantly to your own wallets, adding noise to the transaction history. If there are 500 transactions to white wash the history, then there is little that can be done besides looking through the whole history of the coins - and if there are other bitcoins in the wallet that were obtained legitimately then you might have to search down multiple historical transaction logs for each partial coin.