Ok- I've play(ed) bottleneck slide since I was a kid - you hardcore steelers are going to have to unlearn a lot of things - same as me going the other direction but in reverse if that makes sense
- Robert Randolph often sounds like a rock/blues slide player. I reference his set-up a few times b/c he's the only "steeler" I've heard even getting close. Even if you don't like his stuff, it sits right in there with a cranked Hammond B3, R&B backup, all the rest.
- Tube amp, natural distortion. There are pedals that help but rock slide players if they use overdrive/distortion pedals at all- would do so on top of an overdriven amp. The "lots of clean headroom" is the opposite of what you're looking for. I think if you're serious about sounding like a bottleneck player, you'll need a second amp -kick it in with an A-B switch. FWIW -even the really good dirt boxes like the Klon don't sound anything near the same going into a clean transistor amp as they do a tube amp - even a clean tube set-up like a Fender Twin will give you totally different results than a Peavey Nashville 400 or something. A little Princeton or even a Champ cranked up would be way better.
- Glass slide. That *will* help, if you want to sound like Duane/Derek.
- String Tension - big problem. Need more slop/slink. Perhaps re-configure re-tune your C6 neck with some lighter strings and/or tune down a semitone to B6? Robert Randolph plays a U12 the last I knew. I'm not good enough on PSG to fool with this suggestion yet so YMMV.
BTW - THere is a Robert Randolph "Rig Rundown" on YouTube -well worth checking that out.
- Pickups: All wrong on the PSG. I don't know the outputs/sonic range of a typical PSG pickup but they sure don't sound anything like a 6-string, or most lap steels for that matter. Stomp boxes don't seem to help Robert Randolph was playing a 2-pickup U12 at one point - don't know if he still does but that sounded a lot closer to what you want. Maybe try an MXR 6-band graphic and kick up the mids a little bit - a 6-string has more at 1000-2500 hz.
- Tuning. Derek Trucks plays in open E most of the time. EBEG#BE. That gives you a M3 between 4&3 and a m3 between 3&2...and plenty of power chords R-5-R. That's ideal for rock/blues bottleneck IMO. I played in standard tuning most of the time for convenience -M3 between 3&2 (G-B)- and slant bar to get a m3 there.
- Finger Picks: Nobody I know uses finger picks for rock/blues slide. Hybrid picking (so you could use a plastic thumb pick only) or no picks. Derek goes "bare back".
- Pedals: You gotta stay off them. There's no equiv - Bottleneck players don't have them, so as soon as you pedal into or out of an interval - no longer sounds like a bottleneck player. The best we can do are bar slants.
- Scales: Rock/Blues players play major and minor pentatonic predominantly with the "blues scale" and M9 tossed in. That's a very different mindset than most pedal steel players who play much more melodically. Robert Randolph gets the sound you want sometimes- do what he does.
- Volume knob vs. Pedal. I always used a volume pedal but it is true guys like Derek Trucks don't. They use their volume knob to "clean up" their sound.
Hope these suggestions help someone. I'm a noob on PSG but I got around as a slide player back in the day
. My biggest influences were #1 Duane Allman, Billy Gibbons, and George Harrison, who also got a beautiful sweet tone. Trucks def. has it going on today - as does Susan Tedeschi. Bonnie Raitt is very under-rated. For lap steel - David Lindley, no doubt.