There are many kinds of erotic massage parlors in Düsseldorf and all of them offer more than just a regular rub. The basic package usually covers a handjob but extras can include anything from BDSM, Shibari, full service, pegging, scat, you name it. Bodyfantastic (https://www.mybodyfantastic.de/) at Harffstraße 34, has a regular sensual massage menu, including 4 hands and prostate treatments. Massage Lounge (https://www.massage-lounge-duesseldorf.com/) at Brehmstraße 85a, has baths and a choice of BDSM scenarios.
Erotic massage in Düsseldorf is quite easy to find and of high quality, but the prices can get steep. Prepare to pay around €150 for an hour. FKK’s and brothels are a good alternative as they often also have skilled erotic masseuses available on the spot.