Jacek,
I am using both Khaki Green G3 and SCC2 from Aura design in the Czech republic.
https://www.facebook.com/camouflage.paints
I agree with most others on the U-bolts. Measure them and see if the Filling station or any of the other suppliers have them available. I had the filling station make custom U-bolts for my C8 and that was only a few dollars extra on top of the normal catalogue price. I don't know about Poland, but I was unable to find a local supplier that could make U-bolts in inch sizes and UNF thread.....at least not for a price that would fit my budget.
A few F-clamps is what I used to keep my spring packs together, but than again....C8 springs are not as heavy as C15 springs.
Regarding loosening the stuff. I presume you have tried putting jack under the four ends of the U-bolts (nuts fitted to ends) and than tried lifting the lot? I guess this might not work due to the lack of weight after disassembly of most of the truck....
Alex