Bet the ML on the fav you want. Say the fav is -115.
1.15 units to win one unit.
risk one unit on the fav -1.5 runs at +150 ( or whatever it is).
If fav wins by 2+, both bets win.
If fav wins by one exactly, you break even.
The amount you win on ML, is what you risk on the -1.5 line.