"Archive" solution recipe as used by record libraries stateside and in the UK in bygone times:

25% (max) lab grade 99.9% pure IPA;

75% demineralised/de-ionised water;

Add to this 0.5 to 1% by volume Ilford Ilfotol wetting agent (do not use older recipes such as Kodak Photoflo as the additives could leave a residue).

Personally, I'd avoid using washing up liquid as it contains large amounts of salt but a little (as in a few drops per litre) may be ok.