If Power Bracer multiplies the EVs by 4
I does not Multiply by 4, it adds 4, and Pokerus will double that, so say you fighting Bidoof with one Hp Iv:
1 Hp IV+ Power Weigh=4 more hp IVs, equal 5 Hp Ivs, then, double that, so every Bidoof you kill, gets you 10 Hp IVs.
Hope this helped ^_^