"Bitcoin DNS" is a bit of a misnomer.
It appears that hostnames such as
dnsseed.bluematt.me are not actual DNS servers - you cannot communicate with them using DNS protocols. However they are valid domain names in the normal public Internet DNS system and have multiple "A" records associated with them. You can therefore query the DNS seed hostnames in the normal way (i.e. send DNS queries to your local DNS servers) to get a list of IP addresses that are presumably Bitcoin full-nodes.
You can then, I guess, communicate with any of those IP-addresses using the appropriate Bitcoin peer-to-peer protocols.
Note that some of the returned addresses are IPv6 and some IPv4.
C:\> nslookup dnsseed.bluematt.me
This is confirmed by Bitcoin.org's developer guide which says
When started for the first time, programs don’t know the IP addresses of any active full nodes. In order to discover some IP addresses, they query one or more DNS names (called DNS seeds) hardcoded into Bitcoin Core and BitcoinJ. The response to the lookup should include one or more DNS A records with the IP addresses of full nodes that may accept new incoming connections.
It goes on to describe the protocols that can be used to communicate with these nodes.