Percona XtraDB cluster backup solution

We have a 3 node percona xtradb cluster and two slaves attached to it. One of the slaves we want to use it for taking backups. We have GTID based replication setup between the slave and the Xtradb cluster. My question is if we are adding a new node to the xtradb cluster can we use the backups from the slave and restore on the new node. Also would we be able to avoid SST and do IST instead. I am not sure how that part works since the backups are from a slave. Any help will be appreciated.