You'll never get that sound with a fretted. In fact you may never get it with a fretless. Why would you want to? Then everyone will say you have gas, or call you fartman.
Instead of trying to learn from me, find where I got my inspiration for those obnoxious sounds...listen to side two of Jethro Tull's A album that came out in 1980 (consequently the best year ever for albums to come out), or even listen to anything by Mick Karn specifically an album called Dali's Car - The Waking Hour (1984).
That reminds me...oh, nevermind. When I get the time I'll start a new thread about it.
