Congratulations Wotjek, on this superb result.
I usually buy Pickelhaube in good condition, but sometimes I 'save' some myself. This was the case with this Bavarian Leib-Infanterie that I acquired a few years ago in Ciney. It was so damaged and oxidised that it was still on sale at midday. I didn't re-lacquer it, just put it back in shape and cleaned it. I simply moistened the leather with 40° lukewarm water, then placed the shell on a hat stand and left it to dry for 48 hours at room temperature.
Note:
This is an old schell M1886 (cross base, large front plate, square visor, etc.).
In peacetime, recycling old 86s into dashing 96s, the holes in the old linings were carefully plugged with leather plugs, with a patch of fine basane inside, then the helmet was re-lacquered.
But here we have an ersatz mobilisation. The holes are simply plugged with very light rivets. I have only seen this method used on Bavarian helmets.
