Use vias to route the signal fron the plane to the component.
Do not forget, on the Plane you will require Thermal releaf but on the other layers (that the voltage does not connect to) you will require a region the via that has no copper.
it is always best to have separate layers for power,signal and ground to avoid any type of interference but if the board thickness is of major concern and you want to reduce the number of layers then you can mix up signals with ground but not with power