migrating from sendmail/shadow to sasl on new box

[blast]

As far as I've been able to find, the only way to migrate use info from 
an old box running sendmail authenticating against shadow to a new 
system running postfix authenticating against sasldb2 is to use the 
auto_transition feature.  Is this true, or is there perhaps a 
manual_transition feature that I might employ?

Thanks for listening,

basem