Had more than a handful of domains I needed to add TXT record for in Windows DNS (2003). I did it using dnscmd from 2003 Toolkit and command line.
This will enumerate the zones (I search for Primary and exclude reverse):
dnscmd /enumzones | find /I Primary | find /V Rev > zones.txt
After I have a zones.txt file, I then loop through it to add the TXT record.
for /f %x in (zones.txt) do dnscmd . /recordadd %x @ TXT v=spf1 mx -all