I use the Unicolor powder kit. With the first kit I used the stabilizer as-is and got white drying marks (interestingly, only on 35mm film, not on 120 film). With the second kit, I added 1/2 teaspoon PhotoFlo concentrate to 1 liter of stabilizer and it eliminated the white drying marks. I found I had to add another 1/2 teaspoon PhotoFlo concentrate after 10 rolls of film (I get a total of 15 rolls from a 1-liter kit).
I just happened upon this site and this brings back memories.
I worked along with with Bob Chapman at Unicolor in the mid-70's. There is alot I have forgotten specifically about the various formulas, but K2 stabilizer contained a wetting agent (like Photo-flo), formaldehyde, and probably a pH adjuster.
Soak the negatives gently and allow the emulsion to swell and then use stabilizer. To minimize spotting, you can carefully wipe the negative with a photo-grade spong soaked in stabilizer (but wring out excess stabilizer) to remove excess solution to minimize spots. The emulsion will absorb the stabilizer it needs to protect the dyes.