Whatever approach you choose, you definitely want to know some words with a large percentage of vowels. There are some nice all-vowel words out there like aye, eye, and you. Here is a sampling of some longer vowel-heavy words:
eunoia (83% vowels)
eerie, adieu, audio, bayou (80%)
year, ooze, area, iota, auto (75%)
sequoia (71%)
"Eunoia" and "sequoia" are also distinctive for being two of the shortest word containing all five vowels. "Eunoia" may get you in trouble if you try to use it since it's an obscure word. [I am partial to it because it is a brain word. It comes from a Greek word meaning "beautiful/favorable thinking". The "beautiful thinking" interpretation led to the obscure English usage of "eunoia" - a state of normal mental health. A stricter reading suggests that the Greek word referred to thinking that was favorable to someone (like one's spouse). The "blissful and benevolent state of mind" interpretation, though questionable, is the nicest.]
If you are interested in obscure words on the extremes of human language, check out the All-Vowel Words and All-Consonant Words dictionaries. They start with tame words like "eau" and "brr" and then spin off into highly arcane references (at times approaching Borges-level bizarreness). They come packaged together in a book called "Wye's Dictionary of Improbable Words", downloadable from Lulu for ~$14 or buyable from Amazon for $25