The most effective way is to add 0's to a database record. No one loses any money, so it is easier to hide.
Depending on your access to the database (and resulting reports), an explanation for the source of money will have to be faked. Faking incoming transfers might be as simple as creating a record in the incoming wire or ACH credit transactions. The amount and frequency should not raise any red flags.
Auditors do not normally check deposits against the sourcing bank or entity. For example, you might have a deposit appear to come from Paypal on an ACH credit. It is highly doubtful the auditor would contact Paypal to verify the deposit.
This could be set up as an automated procedure to simulate an ongoing business of some kind. Be sure to pay your taxes on the "profits".
From the bank's perspective, they are not losing any money and in fact, will see your bank account as beneficial to their "reserves". Assuming you have thought through all relevant possible auditing checks, you could simply spend the account directly and not worry about "laundering" it. Alternatively, you could transfer it slowly into gold or out of the country and retire.
A public specification to describe financial transactions goes a long way to solving this problem.