Assuming that you want to pay taxes (even those you probably don't have to because the regulation is unclear),
Assuming that you're rather confident in your exchange, but don't want to risk doing it in one transaction,
Assuming that...
1. Tell your bank about the expected money (make sure they don't reject the transfer)
2. Tell your exchange support about your plan and make sure it is OK.
3. Send btc to the exchange in few batches (few days apart), sell and withdraw immediately to your bank
4. Declare your capital gain and pay taxes
In what country are they going to let you in cashout 500K dollars without paying taxes? Do you really think that the bank isn't going to put their alarms on when they see so much money coming from nowhere? of course you'll be forced to tax it, as far as I know there's no other way around it.