Just an iso booth? No kitchen, living room, etc.? The very essence of bluegrass begs for a group performance, and an iso booth will KILL that!
Try to find a room that they can all be together in and have a little "breathing space".
What mics do you have? Fiddles take to a good ribbon real nicely. It takes some of the "scratchiness" out of them.
As for links, try going to fretsmag.com and look up Scott Rouse's Recording Tips. Even if you can't afford the gear, there are some great
insights.

Go ahead... stick a bluegrass in an iso... they can't play... correction, they WON'T play that way!

The entire essence of bluegrass is group performance.

You need two things... a good ribbon and a good pre.

Set up the mic about chest high/midline of the instruments.

Place the mic in a non-nodal location in the room.

The players will naturally (should) form a semi circle around the mic. Traditionally, they will take a single step up toward the mic for solo's.

Typical arrangement (Left to Right) fiddle, mandolin, bass (in the middle) aco guitar.

I typically put up an LDC for the vox... using rule of thirds... away from the band (if they have a solo vocalist)

If you can set up a decca tree, that works too. If you go that route, just put up a dummy mic in the center (as above) and let em' have at it.

The best is to use a stereo ribbon, as above, and MAYBE augment the bass with a Beta52 or bass transducer.

Good luck, and remember that bluegrass is best recorded as simply as possible.

Best recording I ever did of a Bluegrass band was them standing around in a circle with two Omni microphones in the center. They were self balancing and played well together so my job was made much easier. ISO booths and separating musicians is NOT the way to go for BLUEGRASS or String Quartets (think about the similarities and you will get the idea)

Thanks a lot. I forgot to mention an important detail. There is one main guy playing all the instruments. So I will have to separate it. would room miking all instruments and then panning accordingly be the best way to go? or would close miking work best in this situation. I do not have a ribbon mic but I do have a pair of NT5. C414, MXL tube mic, and a handfull of other LDCs, SDCs and Dynamic mics. If I should pick a ribbon up, what inexpensive, quality options do I have?

Thanks again

My only ribbons have been Beyers. I used to use an M160 ( :( ), now I have an M260. They both do pretty well, but they're hypercardioids. I do have an Apex ribbon as well, but ribbons that cheap aren't really suitable for what you're doing; they're too dark. I like the NT-5's on mandolin, banjo, and guitar. All of these I run through a Grace 101 preamp (NOT the ribbon version). And even if it is one player dubbing everything, pt the player in a big enough space that has some life...

I like the NT5 on the fiddle, but I think I'd choose the 414 for everything else except the vocal. You want the size and space thing as all have been saying so the 414 is sensitive enough to pickup anything clear out to the corners of the room. Omni....of course.

thanks, any tips about vocals?????

Start with that LDC Tube mic you have and go from there. Even if it winds up being a 58 that works the best.

The single mic will not give you the new bluegrass sound, I record grass most of the time, Large condenser on bass 12 to 14 inch off bridge,one small cond. at base of fretboard 10 inches away, place towel or pillow under tail piece if bass if it has low rumble. Fiddle 414- 8 inches above f hole treble side. 414 on banjo since you don't have a ribbon bottom of head 12" away, mandolin 414 and small cond.I would clone each trk. eq and pan second little different .keep bass center.

Just to throw something into the mix, I've been using the D-TAR Solstice on mandolin (using a Schertler transducer) and acoustic guitar (using an LR Baggs i-Beam). I A/Bed it against multiple options including Sebatron DI, JLM DI, the Radial Tonebone and the Bose T1. If you are struggling with sound in the room, this is an incredible unit, its fidelity is just wonderful, and its great for live use. If you want some options later in the mix, I've found this unit extremely useful to put difficult instruments through (mandolin, fiddle, any soloists) as a seperate stem for mix expansion later.

These Schertler transducers are just wonderful, they don't replace a mic by any means but they give you a great direct signal to work with later.

You may want to stop over to the Acoustic music forum and poke around for more info. There's some useful info there on recording acoustic music in general, and a few new bluegrass threads.

If your client is doing it all himself, you may need to work with a click track, at least for getting in and out of a tune or a phrase. (He may also have it so well laid out in his head that he doesn't need it, and he may be a mofo when it comes to timing; but there could be places where a click would come in handy.)

If you decide to do just the 414 in the center, I would recommend moving the player around to different locations for each different instrument and then pan accordingly to make the stereo seperation. I've only ever done that on vocals, but I liked it.

We used one Equation Audio F.20 large condenser and it sounds like everyone is individually mic'd. Google "the Woodpicks, Walkin' In Jerusalem." You should find a YouTube video to give you a sampling of how we sounded.