What effect to use for the scratchy disco guitar sound?

[Funky Dude]

Hi all. I've just recently got a guitar fx program which I input electric guitar or bass to the microphone input on my soundcard and can get some real cool effects including the Shaft style funky wah wah sound I always wanted to do (well close enough to it, may need some adjustments).

Anyhow I'm trying to work out how to get the popular gritty sharp scratchy disco guitar sound which was real popular during the late 70s and early 80s. Examples of the use of this guitar sound in songs are:

Van McCoy - The Hustle (the funky guitar break halfway through the song)
Crown Heights Affair - Foxy Lady (where they sing "ooh you're foxy.... oooh foxy.... oooh you're foxy")
Kool & The Gang - Jungle Boogie
Kool & The Gang - Hangin' Out
Kool & The Gang - Celebration
Diana Ross - I'm Coming Out
Hi Tension - Hi Tension
Haircut 100 - Boy Meets Girl (this one is real uptempo)
Liquid Pleasure - Take A Little Love
Kay Gees - Waiting At The Bus Stop
Tower Of Power - You Ought To Be Having Fun
Van McCoy - Change With The Times
Bonnie Pointer - Heaven Must Have Sent You (this is a classic example of guitar scratchin')
Eastside Connection - You're So Right For Me
La Belle Epoque - Black Is Black (the scratchy guitar break)
Carrie Lucas - I Gotta Keep Dancin' (the rock guitar break)
Con Funk Shun - Too Tight
John Davis & The Monster Orchestra - Up Jumped The Devil
Calhoon - (I Wanna) Dance Dance Dance
James Wells - My Claim To Fame
Chic - Dance Dance Dance
Chic - Le Freak
Chic - Good Times
Wardell Piper - Captain Boogie
Hi Tension - British Hustle
Edwin Starr - Happy Radio
Heatwave - Eyeballin'
Heatwave - The Groove Line
Olympic Runners - Whatever It Takes
Olympic Runners - Get It While You Can
Olympic Runners - Solar Heat
Hamilton Bohannon - The Happy Dance
Gene Chandler - When Your Number One
Queen - Another One Bites The Dust
Kool & The Gang - Funky Stuff
Kay Gees - You've Got To Keep On Bumpin'
Kay Gees - Hustle With Every Muscle

All these songs used the scratchy gritty tight guitar sounds in various forms. Anyhow I was wondering what this guitar effect is called and what sort of effect is needed for it?

__________________________________________________ ___
AUSSIE AUSSIE AUSSIE!!! OI OI OI!!! :D :D :D

[QUINNY]

Funky: It's all about playing the upper strings, a thin EQ and not letting the strings ring too much by only lightly pressing down onto the fretboard with your fingers. No FX as such, just good musicianship and feel.

[Mr.Ree]

I'm not 100% sure what you mean when you say you want to "work out" that sound....does that mean you want to play it or sample it? Anyway, in my youth, I was able to play that sound on my Sears guitar. It just required simple amplification and playing 2 strings simultaneously. My model funk guitar lick records were Zapp's "So Ruff, So Tuff" and "More Bounce to the Ounce" and James Brown's "The Payback". When coupled with an equally funky bass line, the effect was QUITE stanky.