I'm not sure if the virus spreads via breeding.
The rule of thumb is...
1. Place PKRS'd Pokemon in first position.
2. Have it battle.
3. Check team after battle ends. Usually the next 2 Pokemon will get infected.
4. Repeat Step 2 until all 6 are infected.
5. Deposit, and start again at step 2.
Another note. PKRS usually dies out at the midnight it is caught. However, if you deposit the Pokemon before midnight, and then withdraw it after midnight, the PKRS clock is reset.
One last thing, PKRS doesn't spread within the box. You have to do it manually using the above steps.
Posted on: October 30, 2013, 01:50:11 AM
At least this was true for me in Emerald, and Platinum. Not sure if things changed since then.