I use https://github.com/KillerByte/node-merged-pool  at my pool
I don't know how to configure it for merged mining, for example "CROC" coin + "23 Skidoo" coin  (both sha256d algo):
I actually don't know how to make an address for block reward be shared between all coins
I try dumpprivkey at CROC and importprivkey at "23 skidoo"  and I get error "Invalid private key encoding"