It shouldn't damage your emulsion regarding the 50/50 mix don't. Please follow Kodak's recommendation of 98% isopropyl alcohol they know what they are talking about. On what side of the neg did you spray the protectan on the emulsion side or the other side? If you sprayed it on the non emulsion side you can use a cotton swab + isopropyl to clean it. If you sprayed it on the emulsion side it probably better to submerge the neg. Viel Glück