I'd like to add slim line grips to my Kimber compact. The new grips come with shorter screws plus new bushings.
Can anyone tell me how the bushings are kept in the panels? Are they pressed in? Do I need special tools to replace them?

Also, what are the advantages of hex head vs allen head grip screws?

allen head are better because they won't strip out very easy. The bushing for the small grip screw and the regular grip bushing are threaded into the frame. Some people use lock-tite to keep them in place so you may have to heat the bushings carefully before removing them.

Gary

Left hand threads? What does one use to install/remove them?

Quoted: Left hand threads? What does one use to install/remove them?

Grip screw bushings are screwed into the frame and sometimes are staked in place. I've been able to remove all the ones I've come in contact with with a large screwdriver (large enough blade to fill the slots on both sides). They are, or should be, threaded normally (unscrew counter clockwise). You shouldn't have any problems.

Remove old screws, remove panels, remove bushings. Clean where panels were. Install new bushings (with a drop of medium strength loc-tite, blue I think, if you desire). Place new grips over bushings and install new screws. You're done.

Jonathan

Of course they may be staked in, in which case you may have to resort to careful use of a Dremel.  At least it's easy enough to tell whether they are staked: if the back of the bushing and frame have "dents" on them, they're staked.

Not being familiar with how Kimber mounts their bushings, if it is staked or in an aluminum frame, you may just want to thin your existing ones down.
Placing an expendable grip screw from the inside (to protect the threads) and draw filing the bushing to the desired depth to use those shorter screws. Just another option...
Plus, I would hate to see the bushing hole stripped out if they were staked in.
Place the new grip over the "long" bushing to see if it bottoms out against the frame, checking to see if the bushing head is not to thick to do the alteration.

Take it to a gunsmith. There's an awful lot that can go wrong on this job. If you do it yourself, apply some penetrant to the bushing threads 24 hours before attempting to remove them - not WD-40. SiliKroil or PB Blaster, for example. Have a bushing tool (see Brownell's) ready. Look inside the frame to see if the bushing has been 'staked' to the frame to prevent it from turning when loosening the grip screw. If it has, take it to a gunsmith or cut the bushings down as already suggested. If not, go ahead and unscrew them using the bushing tool. Don't play around with them, hit them with all your torque right off the bat. If you have a stuck one and try to use a regular screwdriver on it, you'll probably strip out the driver slots in the bushing. All you can do then is to put a grip screw in the bushing so it won't collapse, and start it turning with a needle-nose vise grip. Like already stated, use LocTite when installing the new bushings, and be extremely careful not to cross-thread them. These bushings are one of the weak points on a 1911. If you strip the threads in the frame, a gunsmith may be able to restore them or oversize them for some repair bushings. They may have to be brazed to the frame, requiring refinishing.  

Quoted: Take it to a gunsmith. There's an awful lot that can go wrong on this job. If you do it yourself, apply some penetrant to the bushing threads 24 hours before attempting to remove them - not WD-40. SiliKroil or PB Blaster, for example. Have a bushing tool (see Brownell's) ready. Look inside the frame to see if the bushing has been 'staked' to the frame to prevent it from turning when loosening the grip screw. If it has, take it to a gunsmith or cut the bushings down as already suggested. If not, go ahead and unscrew them using the bushing tool. Don't play around with them, hit them with all your torque right off the bat. If you have a stuck one and try to use a regular screwdriver on it, you'll probably strip out the driver slots in the bushing. All you can do then is to put a grip screw in the bushing so it won't collapse, and start it turning with a needle-nose vise grip. Like already stated, use LocTite when installing the new bushings, and be extremely careful not to cross-thread them. These bushings are one of the weak points on a 1911. If you strip the threads in the frame, a gunsmith may be able to restore them or oversize them for some repair bushings. They may have to be brazed to the frame, requiring refinishing.

Your scaring me.

I have done this job to several 1911s.  Only one gave me a bad time.  The bushings on that one were held in with red locktite.  It was a bit of a fight, but I eventually won.  The others either had no locktite or only the blue stuff.  No problem with them.  Watch-Six

I've never had a problem removing bushings from any of the older Colts.  I don't have that much experience with the new crop of 1911s though.

Does anyone know whether the thin bushings will work with regular grips if you decide to go back to them?   If so, I would recommend using red Loctite on the thin bushings.  If you didn't want to mess with red Loctite, you could use the blue (which can be broken with a moderate amount of torque) in combination with some anti-seize compound on the grip screws.   I have had more than one grip bushing come out with the grip screw.

Quoted: Does anyone know whether the thin bushings will work with regular grips if you decide to go back to them?

I don't think the grip screws are long enough if used with regular thickness grips and thin bushings.