Hi, here’s an option for you.
3 of us from this forum (we have never met before) are starting the Camino de Madrid on Friday 23 March.
See this thread:
https://www.caminodesantiago.me/community/threads/camino-de-madrid-march-2018.51777/
You are welcome to join us for that weekend!
It will give you a quick introduction to walking a camino, and it would be a perfect chance to test out carrying your backpack.
Either start with us from the church of Santiago & St John the Baptist on Friday morning, or get the train to Tres Cantos on Saturday morning and we’ll meet you at the station. You can then get the train back from Cercedilla on Sunday afternoon.
We are a lot older than you, but you only have to put up with us for 2 or 3 days! Then next time you have a few days’ break (and there’s no snow on the pass to Segovia), you can get the train back to Cercedilla and continue.
Jill