using rpccookiefile instead of username and password for antminers I mine using username and password at the moment but as bitcoin core is changing over to rpccookiefile. My question is, if i use rpccookiefile how do i point my antminers to my local bitcoind 'pool' as the fields on the antminers require username and password ?
The RPC cookie file is only for local authentication of bitcoin-cli.

For external applications, you should use rpcauth= lines in bitcoin.conf. A tool for generating these lines given a username and password is in the repository.