All you need is a chart with katakana and hiragana on it. Then just check on the chart. Chances are it is something simple like Aaaaaa or Gagagaga or something simple like that. Then just see what it sounds like when said. But then again it might not make as much sense as the word in your natural language. But I have found that manga like Lady Snowblood are really dialogue/story based. So if I can’t get the sound effects it isn’t as bad as some manga.
My perfect manga: Speech in English, Sound effects in Japanese (with or without a glossary at the back), all important words kept in Japanese with a glossary at the back (usually for Samurai manga, to explain historic terms and such), honorifics kept (-san, -senpei, -kun, etc) and names spelt last name first as in Japan.
In Japan, I bought bilingual manga (Cardcaptor Sakura; not that butchered piece of crap that is Cardcaptors though) from Kodansha. It had English prominently in the seech bubbles, but also Japanese in smaller text next to it. The sound effects were in Japanese with English on the sides of the page. That was quite cool.
