Do we always need a “rhema” or a leading from the Holy Spirit before ministering healing?

Let’s look at the ministry of our Lord Jesus. Scripture does not explicitly record that he always waited for a leading from the Holy Spirit before healing the sick. Therefore it’s actually an assumption on our part that he did. 
When Jesus sent out the 72 disciples in Luke 10:9, he commanded them to “heal the sick who are there and tell them, ‘the kingdom of God has come near to you.'” This was before they received the Holy Spirit. Therefore whenever they proclaimed the kingdom of God to the lost, they were first to heal the sick. This therefore was not dependent on the leading of the Holy Spirit. 
In Acts following Pentecost, the disciples generally followed the same pattern. It is not explicitly recorded that Peter received a leading from the Holy Spirit before healing the lame beggar at the Temple Gate in Acts 3, or healing Aeneas in Acts 9. Yes, before Peter raised Dorcas back to life in Acts 9 he did in fact pray. So it is possible that since this involved raising the dead—a rare and extraordinary miracle different from healing and which Peter did not often do—the Holy Spirit spoke to Peter as he prayed. And Paul did pray before healing Publius’ father of dysentery in Acts 28. But we are only assuming that Paul was asking for the leading of the Spirit as he prayed. He could have simply been asking the Lord to heal the man before actually laying hands on him to perform the healing. So we can reasonably conclude that while it is wonderful to have the leading of the Holy Spirit before healing the sick, it is not always necessary—especially when the context is sharing the gospel. We and the very many disciples we have trained over the past 40 years have healed those who come to us without a direct leading of the Holy Spirit on many, many occasions—leading to people accepting Christ after the gospel is preached.
One notable exception is Paul being filled with the Spirit in Acts 13 before cursing Elymas with blindness which then led to the proconsul believing in Jesus. It is notable that this particular miracle did not involve healing, but rather the opposite.
According to 1 Corinthians 13, the primary purpose of the gifts of the Holy Spirit, like the word of knowledge and the gift of healing, are building up the body of believers. When ministering to believers who are accountable to God, it is good to have insight as to the spiritual condition of the believer. For example, does he or she have unforgiveness or bitterness in their heart—which can keep the believer from being healed? Therefore James does teach us to pray for one another.
But when preaching the gospel to the lost, there are no such conditions in order for the sick to be healed. Rather, the miraculous healings are used to draw them to believe in Jesus Christ!
It’s wise to be impartial and to follow Scripture literally when studying about miraculous healing. We shouldn’t always make assumptions about what Scripture teaches—which could led us to unbalanced understanding and limit our effectiveness in ministering healing to the sick.