I have done it the way you said- transfer 100% of the money to the broker' escrow account before the seatrial. But I knew the broker personally and had no qualms.
A cashier's check isn't quite as good as a wire transfer. Many brokers will hold up funding
until the cashier's check clears. I know, I worked for one and they did hold up funding
A wire transfer costs about $30 and is as good as gold once it clears. If your bank has a branch near the broker then it is easy. If not then stop by your local branch and set it up in advance so that you can fax the wire instructions to someone at the branch who knows you and will process it.