Many soldiers can disassemble and reassemble their guns blindfolded, but for the average soldier, the only guns they have access to are their issued primary weapons. After a period of time, even without deliberate practice, they become extremely familiar with the weapons in their hands.
Paul was different, he brought six pistols, and he had mastery over all six of them.
Pistols are small, and their parts are even smaller. It is even more difficult to distinguish all the parts when they are mixed together. Not to mention, the six barrels, similar in thickness and almost the same in length, have very subtle differences. It is impossible to categorize them the instant they are touched without being extremely familiar with the guns.
What Paul demonstrated was not just a familiarity with guns; he showcased the pinnacle of a gunman's skill.