OK, you’re relying on this cylinder to stop you and the bike, instead of using a stationary object to slow you down when you hit it. I would take the slightly longer winded method of strip down and check it before fitting, and maybe just resealing it as a precaution.
Where brakes are concerned cutting corners is not a good idea.
Having said that, Laudanums method will work, and you don’t even need the hose, just put your finger over the hole where the hose goes in, pull the lever back, and you will feel the pressure but you shouldn’t be able to prevent it from getting out past your finger. Wearing gloves is also a good idea as brake fluid is a nasty substance for sensitive skin. Make sure to avoid getting brake fluid on paintwork, as it makes very good paint stripper.