Hi,
I just dit CF on Mountain Bike all the way to Finisterre.
If you are walking the CF ( +-35days) ... rather take the Bus ( 9.90€ ) to Finisterre instead and spend the extra day or two there reflecting/ recovering
Then, on return go via Muxía with a 20min stop at the point / Cathedral en route to Santiago ( also 9.90 € ) or stay there for day or two.
Finisterre was a definite highlight and appropriate way to soak up my experiences on CF and spend good time with fellow pilgrims watching sunsets from the lighthouse and Sunset Beach.
I can recommend Albergue La Spinals .. really great place 13€ per night or 30€ for private Double room.
The hassle of bike hire .. Panniers ... and depending on fitness .. also .. the road option is boring .. so a mountain bike for the trail should be your only consideration if you insist on not walking or bussing.
Hope it helps
Buen Camino