As for my opinion it is close to american sounds /i/ in the word /topic/. I know a simple exercise to make sound /Ы/: Take a pencil between your teeth and try to pronounce letter /И/ :)

it is not like Й ы - is a particular sound, that should be trained as much as others. Russians destinguish difference between vowels: и (don't confuse with consonant sound й) and ы. The articulation of Ы is almost the same like И, BUT the tongue should be relaxed, moved a bit backwards and not press the lower teeth. Try to pronounce Мы, Вы. Listen to some audio recordings that you like and pay attention on this sound.

I think the closest sound in English for /ы/ is /i/ after /th/ like in 'this'.

It sounds like a punch in a stomach but loong