Looking for advice from those that have walked in Scotland
I come from the Scotland of the south, and hope my experiences might assist.
As I arrived at Saint-Jean I had been just over three weeks on the way from Le Puy-en-Velay with a similar elevation gain on the first day, but at a more gentler rate of climb. So I was match fit for the pull up to Orisson, and others a bit later.
If you are near Edinburgh, my father would have recommended regular walks up the Pentlands, or even Arthur's Seat. Do those trips often enough with all your gear will get you match fit as well. And your legs will get used to the climbing and descending (just as many hills to go down in Spain).
Being match fit is essential but wait, there is more.
After 3 plus weeks I had become acclimatised. The early May morning of leaving Saint-Jean I dressed for the late morning weather. For me that was a short sleeved merino top, light weight kilt, long hose, gloves as my fingers get cold very quickly and a floppy hat pulled down over my ears. But my body warms up quite quickly. When underway I noticed many walkers stopping, take off an outer layer, open their pack and put it away: I am sure they got a bit of a chill in doing this.
A trick I had learnt in my four years of training before I could leave home, was this: as the road steepened I would shorten my step and keep the same rate. On the flat my step might be, say, 700 mm (2 and bit feet). On a really steep section I would reduce my step to about 1/4 of that, say 150 mm (6 inches, or about half a foot length - as the right foot landed the heel would still be well behind the toes of the left foot). I would keep the same rate of foot fall and I would consciously breathe in on one footfall and out on the other.
With those two techniques (plus the fitness) and with three stops - 3 minutes at Orisson to ask about the weather, 30 seconds at Last Sello (bitter wind and no Sun) and loo stop on the descent - I noticed only one person passed me when I was walking.
On day two I reached the hostel at Zalbadika. This is a parish operation with same Sacred Heart Sisters providing a pastoral care. In the evening service were were asked to share our experiences so far. I was most surprised when the young 20 somethings asked me why I was "so fast". I explained the above and they were content. The next day I was the far side of Pamplona, trying to get a landscape photo of the "windmills" when another 20 something asked if he could take one of me in the foreground. When done he explained he had heard about me that morning.
That's quite a mouthful, sorry. But, in my view, it is not how many Munros you walk up but how you are prepared in all aspects that will ease you way up and your way down.
As Her Majesty says to us Scots and others of the south,
Kia kaha, k
ia māia, k
ia manawanui (Be strong, be brave, be patient). To which I add
Get going when you can.