Instead of mucking about with test strips, try using a whole sheet of the size you're working with as the test strip, this way you get to see the full picture of where you may need to dodge or burn along with a time-guide..not really wasteful as it gives more than it takes...also you must use the same paper to test with as you're intending to print with..too many variables involved otherwise. Re flattening fibre paper...buy a couple of glazed, totally smooth floor tiles, size depending on what's the largest size you'll be printing on..glue a handle into the rough size of one of the tiles...wait til the prints are absolutely, totally dry, place tile glossy side up, the place a sheet of very high quality artists blotting paper on tile, place print face up or down, doesn't matter, place another sheet of blotting paper on top of print and finally, place the second tile, glossy side down, on top..leave for a couple of days, life off top tile with handle on and you'll have prints that will be prermanently flat ...best of all the cost just a few bucks. I press 3 or 4 prints at a time, using 500mm x 500mm tiles, nice and heavy.
Oh, and welcome to the world of fibre printing..its magical and very satisfying.
Trisha