I can truly recommend Testors Dullcote Lacquer (no. 1160) which gives really flat/matt protective layer to painted figures.
The only , small disadvantage it is not an acrylic lacquer, so instead of water and soap you need a special thinner/cleaner or acetone to clean brushes after usage.
For bigger models I use Vallejo Matt Varnish in spray which works fine , but only when applied in very thin layers and in moderate temperature and humidity room (never outside the house in hot days or in cold winter as you may destroy results of painting just in few seconds...).
And I confirm what Dead Marsh Spectre wrote above in point 3. If you really aim for solid protection of paint before stripping , you should cover painted model with glossy lacquer first after a day, then let it dry for at least another 24 hours and then repeat the process , but this time with matt varnish.
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Greetings from Dark Side of the Moon
Mars_2000
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My WIPs