Hmm. That trick did not work for me.

I guess it is delayed because slush can not move our payout money from cold to hot storage for a descent fee due to extreme congestion. (Because following remark is on their help page:)


Delay in Payout.
For security reason pool uses two wallets – Hot and Cold.

The funds immediately available for payouts are kept in a Hot wallet. This wallet has quite a low balance for security reasons and when it becomes empty, the pool administrator has to load it from the cold storage – a highly secured offline computer keeping pool's bitcoins. Since this process can not be automated and only very limited number of people has access to the cold wallet, it can introduce a few hours delay in sending bitcoins to user's wallet.