Defensive Pokemon aren't good in playthroughs at all. Toxic stalling each of your opponent's Pokemon is inefficient for a run, as you could just 2HKO the opponent with an offensive Pokemon with better stats. Dusclops, much like all other defensive Pokemon, is bulky and has bad offensive stats with low Speed, you'll be better off using Absol and giving it the Shadow Ball TM, as its combo of Swords Dance + Shadow Ball is deadly. (As in Gens 1-3, Ghost moves are always physical.) Many other Pokemon can pull off the move combo too.
However, if you insist on using Dusclops, here's the moveset I'd suggest for it.
Dusclops @ Sitrus Berry
Ability: Pressure
- Shadow Ball / Shadow Punch
- Toxic
- Protect
- Filler
Shadow Ball is STAB which can work off Dusclops alright, albeit outclassed Attack stat, while Shadow Punch can be used on Dusclops if you want to use the Shadow Ball TM on another Pokemon. Toxic and Protect allows you to Toxic stall the foes you can't deal much damage to, and the last slot can either be used as desired coverage or an HM move.