Genuine question. How would a transition to socialism work in practice?

Generally, Leftists believe it can only happen via revolution. The general idea is to organize and build dual power, so that when an inevitable revolution arises, the working class is already organized and can replace the former state.

Eating the billionaires and "nationalizing" publicly traded companies is the easy part. Saying "you can still possess your car" is also easy. The hard, and ultimately unpopular, part is everything else in between. Summer cottage? Family farm? What happens to pensions/retirement savings, land ownership, inheritance, small businesses, the apartment your are renting out to pay for your own rent...

You're working off the mindset of maintaining Capitalism and piece-by-piece Socializing it, which is not what Leftists generally propose.

I suggest reading Critique of the Gotha Programme, if you're genuinely interested.