No special detergents?
It seems like the Bendix could happily work with soap in its day, just so long as Madam was very careful with dosage. The instructions seem very explicit in dosing soap (and water softener if needed). The warm rinses would also have been beneficial if not very necessary to deal with using soap.
It's a bit like using high-suds powder in an automatic now: you can get away with it if you're sufficiently light-handed with the dosage; the problem is, however, that dosage may be so low as not to have adequate surfactant in the wash water to provide good cleaning.