Sorry to say but I must agree... Irr. Verbs must be memorized.... but that doesn't mean you have to suffer saying them.
Here are some ways you can learn how to say them.
Find a native speaker of the language and ask he /she what they do with their tongue, lips and teeth when they say the word for example
the word went: I puker (like givng a kiss) my lips in the initail sound /w/, then I smile for the vowel sound the tip of my tongue is behind me teeth /e/ for the /n/ sound the tip of my tongue touches behind my top teeth and I release it for the final sound /t/... try it... use a mirror see if you are doing the same things I am.
Another way to practice saying these words or any English words is taking a theater class... yes an acting class... you'll have fun, practice the language, perfect you pronunciation and articulation and who knows you might be the next Hollywood star.
you can also use the Longman Pronunciation Dictionary it's very easy to use and it expalins itself quite well.
What ever you do keep working on it... practice makes perfect and it will never hurt..