The Bible never teaches us to pray ‘for’ faith. Yes, seeking Him in prayer is a necessary part of growing faith in our hearts, but the seeking is to be on behalf of the desired answer, not about faith per se. We grow faith by planting the ‘hopes’ of God’s word in our hearts, that is, the promises in the Bible that are pertinent to the answer we are desiring.
Even though we grow faith in our heart by planting God’s promises (and watering it by walking clean before Him in the Spirit), it is God who gives the ‘increase’ to the sown seed. God is the one who turns seeds into harvests. Again, let me make this point very clear; we do not grow faith independent of God. We do our part in obedience to what the Bible says, but the final moment when faith comes alive in our heart is determined by Him, and its life is given by Him.
Once faith is achieved, we are to release that faith verbally by either an asking prayer, or a declaring statement. The Bible only guarantees that prayers of faith will be answered, not just any prayer or declaring statement, no matter how needed they are.