Practice? the Soviets did not consider it a matter of diplomacy not to practice espionage techniques on unimportant foreigners. As a result, when my family was there on academic visas while my father was on sabbatical and working openly on a book for use in US universities, we were often followed and spied on by very new and amateurish recruits whom we could spot in a second. They were out of a Austin Powers movie sometimes. I remember one guy who, when we turned around and looked right at him, reached up and pulled tree branches over his face.
Also, we knew our hotel was bugged, and so my parents defeated it by writing notes on those magnetic erase boards that you could buy as erasable doodle pads for kids. Not that my parents had anything to say, they just liked the idea of using something so lo-tech to defeat the empire.
And the KGB used regular people, non agents, as informants, and gave them stipends. We knew who was informing on us, because again, we were practice targets. In the Soviet Union, they didn’t have merit pay raises. You got paid what everyone got paid for a job. But people who were very conscientious workers might get selected for informant work, and pick up extra money, and maybe luxuries, like use of a dacha that belonged to the government, or vacation time, or travel visas to resort areas.
The civilian informants left the hard core work for the full-time agents, and the extra practice, as well as the ability to integrate full-time agents into daily lives went a long way. That was another thing. With the different nationalities involved in the Soviet Union, plus the bloc countries, someone having a not-immediately-identifiable accent wasn’t a drawback. Someone whose Russian wasn’t perfect might be Estonian, or Georgian, or Czech, and so no one blinked. Someone in the US claiming to work for the CIA evoked suspicion if he had a French accent, or a Mexican accent.
The KGB got over sexism (albeit, not many other -isms) before the US did, and used women agents to great advantage, back when the US thought putting women in dangerous situations was barbaric.
The KGB was good at recruiting, because the earning potential of a job was not a selling point, but its status was, much more so than in not Marxist-aspiring countries. A lot more people wanted to work for the KGB in the USSR than wanted to work for the CIA in the US.