I had this dictionary when I first went to Korea and it has a fantastic list of English words matched to the Korean sounds, so I never had any trouble with anything other than the eu/으 sound. After a decade of living in Korea, textbooks, phrasebooks, studying at university, that was still my go-to book for little grammar tips. Unfortunately I loaned it to some girl who first arrived and never got it back.
These days Ive gotten pretty lazy and my wife gives me no end of shit about it, so whenever I have to use a double consonant, I make sure to say it like I'm taking a massive dump at the same time to really emphasize the sound.