Additionally, if you have an English word and you think it may have a gairaigo equivalent, will pronouncing it in a "more Japanese" style make it easier to understand?
Absolutely. There's a linguistic thing going on here whereby sounds outside of the language you grew up speaking are much harder for your brain to process. This is why certain English sounds (such as /r/ and /l/) are hard for the Japanese brain to process, and why certain Chinese sounds (/chī/ comes to mind) are difficult for the English brain to process. Also, since many Japanese learn the "Japanese pronunciation" of English in school (which is often closer to gairaigo than English), as long as you pronounce your English in a Japanese way, chances are good that they'll understand.
Certain English speakers neglect this step with gairaigo and insist on pronouncing things the "English way", so they end up with sentences like 「昨日、golfをしました。」. This actually hinders understanding, because Japanese people are more accustomed to hearing ゴルフ, not "golf". So although you may weep inwardly at the butchering of English that goes on in everyday Japanese (I know I do), if you want to be understood, you have to follow the crowd and pronounce gairaigo in the funky Japanese way.