>>14536568Excuse me sir, but unless something changed and I missed it, Pokemon which have had the Pokerus will ALWAYS get double EVs, even if it goes away.
The only thing that changes when it goes away is that mon can no longer spread it.
OP, put a box junk pokemon in your party, preferably adjacent to manectric. After a few fights, you should see the Pokerus has spread.
Simply stick that mon back in your PC box. Whenever you want to EV train, you pull the mon with active Pokerus out to spread it around, then stick it back in the PC.
Manectric himself will eventually get over the Pokerus if you leave him in your party, but even after he's over it, all EVs he earns will be double (note: still 510 max, he just earns the max more quickly).