Would there be any safe way of transferring funds from say pokerstars to Fulltilt without waiting 15 business days to receive money from a withdraw? Should I just suck it up and wait?
The fastest and safest would be to create a moneybookers account, withdraw to moneybookers, and upload with moneybookers. I don't think you'd pay any fees either.
Outside the US, definitely use an ewallet such as neteller or Moneybookers. If you are unlucky enough to live in the land of the free try sendmychips dot com. Seems sound, but I have not used it myself (I have Neteller).
The only other way to transfer site to site is to use the 2+2 Transfer Thread. It is generally free (as long as you dont have to pay someone "vig" to get a trade done) but you do need to read the rules and do a bit of research which is spelled out for you in the introduction to the thread.
They transfer hundreds of thousands of dollars so it is used by many players.
Suck it up and wait. I used to work in the Fraud department for FTP and even the guys who would transfer funds legitimately would occasionally accept fraudulent funds unknowingly, resulting in all monies seized.
The ONLY safe way to transfer your funds is unfortunately wait through the withdrawal/deposit process.