Black Sludges on Trubbish

[OverlordDerp]

I know there's a 5% chance or so of getting Black Sludge from Trubbish. My question is, will every wild Trubbish regardless of location have this chance, or will very early places like South Peridot Alley (before beating the first gym) not give you that chance?

Also, on the off-chance I do find one with Black Sludge, will a wild Trubbish use it in battle visibly or will I have to catch it and check every time?

[Khayoz]

Should be all Trubbishes

[Crimson]

you might want to bring a pokemon with FRISK ability in your team it might actually tell you if the trubish you encounter is holding an item

[ShatteredSkys]

Here's an easy way to do it, get a pokemon with frisk (the event shuppet can get it) and a pokemon with the compoundeyes ability (butterfree and venonat are the most common) knock out the compoundeyes user and put it first in your party. If a pokemon with compoundeyes leads the chance of held items on wild pokemons increases so it'll be 20% instead of 5%. Go to the back alley in the first city and with a pokemon with sweet scent and spam sweet scent until you find a trubbish with a black sludge. Don't bother with the wastelands I tried there it wasn't fun.