Masking Fluid + Calligraphy Nibs Leads to Batik-style Painting

I love the look of either white or black lines in watecolor sketches and paintings.  I have in the past played around with masking fluid to preserve white lines, sometimes with a liner brush and sometimes with a ruling pen, not always with good results.  One of the keys to success is a good-flowing masking fluid, and after trying several brands, including Masquepen, I find that I like Pebeo Drawing Gum the best.  But the other key is a good tool that enables me to draw fine lines with the fluid, and I have a new tool that works pretty good.  I recently bought a Brause Calligraphy dip pen set from Goulet Pen Co., and I found the idea online of using calligraphy nibs to write in masking fluid.  Oh, I had to try that.  So I got the bigger round nib in the set, the Pfannen nib, and gave it a go.  With the disadvantage of using masking fluid that is already coagulating in the bottle (it must have been sitting on the store shelf for awhile, usually a brand new bottle is nice and homogeneous with no clumps), I was able to get the pen to work pretty well and draw smooth lines (for the most part).  You do have to keep on top of making sure your nib is filled with the fluid, and do the usual things like pre-dip the nib into soapy water and clean the nib often in the soapy water and wipe clean.  But with patience, and practice, I think this could be a good combination.