DNS settings in Aegir
Check out item 2 on this page on setting up sites in Aegir.


  Login to your DNS control panel at your domain registrar, or wherever
  your nameservers are, and setup the DNS for the domain name to point
  at your Aegir server. It's worth including a wildcard record - ie an
  'A' record for '*' to resolve to your aegir server - then you can
  easily setup new sites on subdomains without having to ever setup DNS
  again!


This video also looks pretty neat, not sure how much it'll help though.