Setting the activation password is the easiest in my opinion. The alternative to this is to plug the phone into the server via USB and letting the BES detect the phone.
You do not specify as to what version of the Blackberry you are using. To wipe the handheld of a curve 8330 you go to options > security options > general settings and the click the key to the left of the trackball. Then select Wipe Handheld. When wiping the handeheld, you can wipe the entire phone, or just the phone and keep the applications installed.