That really sounds like my situation with my 5/8 Thiers-Issard. A superb piece of craftsmanship but even after beeing treated by 2 well known honemeister, can't get a shave with it.

Thought my technique was bad and got discouraged until, one day, decided to buy a cheap disposable straight (Ustura). What the heck, its only 20$?

Well, the surprise is that I could get a babyskin after only 2-3 shaving sessions with this instrument.

Good luck...