DNS Lookup for BDC

How can I locate a host that is an authority for a specific NT domain
name (or realm name)? This used to be done using a 0x1C WINS query for
the NT domain name but since WINS is deprecated I would like to know
how to lookup the BDC or PDC using DNS.

I know the KDC may be located using the realm in an SRV query for:


and I know Active Directory may be located using:


but is it always ok to query these machines for mundane SAM account