in my canoe tripping area,where i would expect to have to do this,i have heaps of birch bark and pine.both are easy to light.
however the first step is to get the moss and wet rotten bits carved off and under some sort of shelter until i would be ready to light it.now the "best practice", i would remove my shirt or jacket to make a rain proof roof and getting close to the tinder pile by laying on my stomach with the "roof" over my head and the pile just in from of my nose strike and light whatever fire maker i have and hope for the best.with birch bark it's a very-very good chance you will get a fire.ok,so now you are wet to the skin but with a blaze going you can dry out.leaving your clothes on in an attempt to stay a bit dryer and not using them to make a "tent" will reduce your chance of success.getting a roof you have ready over the fire is the next step.any sort of tepee made from branches and covered with whatever you have or picking out a shelter place before you start is of course part of the project..just work quick.
some years ago i was up on a canoe trip when a severe,long term storm dumped some 11 inches of rain.i just went to the tent and lived in it until it was over.a few days later i came on a campsite that had been abandon leaving piles of gear all over.i could see that whoever was there tried to make a fire in several places,all failed because they stayed in the open near the existing fire place rather than find a more sheltered spot.among the things they did was make a small "house" from slabs of slate to keep the rain off the tinder pile.it failed because they had such a small pile.there must have been 20 burned out wood matches laying next to it.they could have used the bottle of cooking oil they had to help start the fire like i did when i cleaned up and burned the mess with it
another 1AM run-on post...sorry......