I'm not certain how much "luggage" you want to take. What we did was fill our backpacks with all they would hold, minus any liquids and things that won't go through security. We wore regular tourist clothing for the flight over. We then had a cheap gym bag that we put our stuff that wouldn't go in the back pack, such as collapsible hiking pole, umbrellas, extra clothes. We checked the bag at the airport and picked it up upon arrival at Barcelona. We spent several days in Barcelona before our Camino and spent several in Madrid after the Camino.
After arriving in Barcelona we had regular "street" clothes to wear as tourists and then when finished, we left those at Roncevalles as a donation for someone else. They were clothes that we pre-planned to be rid of rather than carry them.
It all worked rather well and was probably far cheaper than shipping or storing items in Spain.
Dennis "K1"