Thanks for the advice man.
The big problem I've had with most academic eartraining exercises is that I don't really have a natural singing voice, and coupled with that I'm a pretty heavy smoker, so that's limited me a lot before.
I used to just practice singing intervals as well, but I've sound solfege helps internalise them better, so they become instinctive. May have helped that I spent about three years using the approach you describe.
I kinda wish I could start proper study again, but unfortunately the music department at my university closed last year.
