And at the Transfiguration, Christ conversed with Moses and Elijah, long dead by earthly reckoning. He is not the God of the dead, but of the living.
But this does not mean they have authority to help us.
The point of that scene of the transfigured Moses and Elijah may be opposite of that which you intend...the point was to censure Peter when he mistakenly gave Moses and Elijah too much attention...and God certainly never told Peter to pray to them.
It's so easy to depend on other sources than God in prayer. As I pointed out...this is common in religions like Buddhism and easy to slip into..it dilutes dependence on God and it's easy to go from there to idolatry.
However, Jesus told us how to pray. He never told us to pray to anyone other than God.