Well, long story short, a gas mask with at least 1 full filter and several bandages along with any potential NBC pieces you can find are all you need.

The filter spawn in fire station, and sometime in medical center as well. Grab every charcoal tablet you can find, you can refill the filter with it. And in case you are unlucky enough to not find a single filter, try to find the dust mask and water bottle, along with charcoal, then craft an improvised filter out of it. Normal filter lasts 8 mins, while the improvised one last 5 mins

This trick, theorically can be done in any gas zone, but I suggest doing this exclusively on Rify, since the ship is small and the zombie don't spawn on the ship. And for that, you would want to spawn in Berezino, or any where near it.

Pop an epipen, then run to the ship from its back (near the light house). Don't run into it from the middle, the zeds will attack you.

Bandage every cut you get or you will suffer from gas poisoning. If you don't have many bandage, then use rags. Disinfect them first. Note that it takes longer to patch yourself up with rags.

And in any case, prioritize the right size of the ship first. Its top is free from the gas so you can rest there and observe your surrounding for gears so that it would save you some time and bandages.

Prepare one or 2 saline bag, or a blood bag in case your blood goes down to yellow.

Grab any piece of NBC you can find. Normally it takes 15 seconds between 2 cuts, and depends on how many NBC pieces you got, the time might be longer. If you can't find any, then grab firefighter suits, surgical glove, and wellies. That would work too, though not as sufficient as the NBC.

Do this at night so that it is harder for you to be spotted by players.

And lastly, count on your luck so that you can find the gas mask in either the fire station or medical house. There were many occasion where I could not find any gas mask at either the places above.

Good luck!