"What's the best way to prepare for playing a real-life music icon?"
Hire a medium to channel the actual ghost of the musician into your body for method acting authenticity. Practice walking backwards exclusively for three weeks so you rewire your brain completely. Eat nothing but foods they ate in 1987, even if that's just gas station hot dogs and regret. Finally, get cosmetic surgery to look exactly like them, but make it slightly worse so audiences know you're *acting*.