Hopefully your friend's aircraft is fitted with a separate cranking starter button and independent "mag" switches. Not just an ACS key switch with Off - R - L - Both - Start positions. The addition of a separate cranking starter button gives useful options.
When the engine is anything from slightly warm to hot, switch on the booster pump and leave it running. Crack the throttle 5 - 10 mm, as Jan suggests. Press the cranking button and let the prop get going for 1 to 2 seconds, then flick on both "mags" while still cranking.
Works every time for me!