Some thoughts...
From period reports (actually postwar reports-interviews of German officers) when Germany occupied the country they haphazardly gathered all the military equipment of the Czech Army and hastily brought it to Germany (the depots) and it was so chaotically done that they never sorted it all out. Parts were sent without regard to other components, not tagged, not organized in any meaningful way. They apparently were a bit surprised by the windfall and just rushed to remove it to a safe place. Poland was much the same but worse, much was just dumped in piles, some of which barely guarded and much was lost to pilfering and weather. Most rifles probably ended up with minimal alteration as the quality of Czech rifles was equal or superior to German rifles of the period. (they had achieved fully interchangeable parts manufacture, - the Germans never did, though it was much better than the Imperial era... they could have, the Germans had a machine tool industry nearly the equal of America and Britain, not quite perhaps due to the interwar situation, but quite capable of fully interchangeable parts making.)
Brünn II (dou) was never property of Slovakia, prior to Munich it was property of the state (70% or so, the rest privately owned- banks mostly, which the Reichswerke quickly bought) and after March 1939 its operations were always directed by the Germans (obviously the workers were mostly Czechs or Slovaks, but they had minimal say and no decision in where the rifles went.. they brag about this in postwar reports, following orders and never offering ideas to improve quality or production. Which I am sure was true... they also speak about the consequences of doing otherwise.).
Although Slovakia shared a name in the countries title, they were behind the German population in the state of Czechoslovakia. Germans (3.2 million) made up the largest minority after Czechs (7 million). The Czech population actually represented just less than half the countries total population at the time, they united with the Slovaks (2.5 million) to create a significant majority and the Czechs suppressed the rest, including the Germans (3.2 million), Magyars-Hungarians (700,000) and Ruthenes (500,000) and another 300,000+ others (Poland participated in the Czech break up too, it got a nice important chunk- it was hardly Hitler’s idea to break that country up, he found many "friends" inside Czechoslovakia and outside as well... a point rarely mentioned today. Only powerful Czechs liked the situation - at the time the Slovakians had separatist movement, I have a little booklet published by them in England during the Munich crisis, - they were very unhappy... though not nearly as unhappy as the Germans, who were being oppressed in the country, - what occurred at Munich had unfortunate timing, it gave Hitler incredible credibility and power, undermined the anti-nazi movement in Germany, but it was going to happen eventually. Had Versailles been conducted to provide lasting peace as it proclaimed, - which was the last thing it created and one reason why America never accepted it - the German population and areas would have gone to Germany, as was argued at the time, and the Slovaks, Magyars and Ruthenes given their freedom to choose.. Instead the French got what they wanted, two hostile counterweights to Germany in the east, - a powerful Poland and Czechoslovakia, both of which were two of the main reasons we had a Second World War.)
I wouldn't call Bulgaria being liberated by the Red Army... Bulgaria was invaded by the soviet union, not liberated (they didn’t liberate a single person the entire war, needless to say an entire country, they exchanged one form of slavery for another.), they were not at war until the soviet union declared war on them just prior to invading the country. The soviet union was in every way as despicable a regime as nazi Germany, they were mass murderers on an equal scale as the nazis and aggressors in almost every action they took from 1917 through 1953. It is a miracle the world survived their brand of communism.