I hope to use regular garden soil instead of fir bark, and either corse sand OR decomposing gravel. I couldn't find vermiculite, dolomitic lime or gypsum.

Not all are the best on hand items for succulent re-potting but if it's all you have.

Potting soil sift though the potting soil use sizes after sifting of 1/4 - 1/2 inch

vermiculite, dolomitic lime or gypsum: Nothing to worry to much about of all three or either item , you can forget about vermiculite your succulents will be much better off with out it.

Not certain of your succulent types but dolomitic lime and gypsum regarding Ph. increase in other soils or sweet soils for succulents has me thinking that you may have read to much into what Al offers.

I'm still thinking it will be better than the peat-heavy soil they are in now.
ABSOLUTELY Even better is you are more right than you think

Sounds like a reasonably good with a free draining mix 1-1-1 course sand and decomposed gravel with the soil you sifted with some rinsed sifted perlite cut the sifted potting soil to a 50 50 mix for any of the ones in 1-1-1

A small shopping list for the near future:
Fir fines or small sized bark chips
In order: Any one item of MVP Turface or All Sport NAPA Oil Dry , Napa floor dry

For the long haul add to list : Pumice, dry stall, turkey grit.

Would the benefits of repotting early (indoors, with a grow light) out-weigh the idiocy of repotting in the dead of winter?

They're your plants but if they where mine and in a heavy soil like you described it's getting done regardless of how much one weighs or thinks.

If your growing plants under florescent light a full spectrum bulb (6500K) is closest to actual day light.

I just bought this http://www.amazon.com/gp/product/B001LXKGOA/ref=oh_details_o01_s00_i00 it should arrive tomorrow it's very similar to Al's mix.

I have re-potted many plants in winter; is it the best time no. But one does what must be done!

To add to what Wes said: NO garden soil, NO vermiculite.

I'm not sure where folks are reading about vermiculite, but it has no part in a Gritty Mix.

If you use those ingredients, you will have a soupy mess.

Josh

Once - a long time ago - in one thread - I suggested a small fraction of vermiculite in a gritty mix for one grower who was convinced her succulents were going to die if she couldn't build 'extra' water retention into her soil ...... and for some reason, I think that half the people who try to do any sort of research on the gritty mix stumble on that one thread. ;-)

I bought 2 - 2 gallon bags of vermiculite about 15-20 years ago. I make a LOT of soil in a year's time, using a lot of different ingredients, but I still have at least 3 of the 4 gallons of vermiculite I bought way back when. I just don't use it, and can't think of a good reason TO use it in container media.

Al

I live in an indoor desert, and I don't even like vermiculite. It has no structure-holding ability, and forms a mess sooner rather than later. If a person really needs that extra moisture retention, I'd suggest more of a cross between the Gritty and 511... or something along those lines. Though, why anyone would need more retention for succulents is something I don't really understand.

If a grower uses the proper ingredients, of the proper size, prepared as directed, and used as suggested, there really shouldn't be any issues. There is a short adjustment period for the plant, and also one for the grower... but if we're being honest with ourselves about not taking any shortcuts, and making sure we understand the concepts involved in using the Gritty or 511 Mixes, we should be all good.

I would only re-pot in January if the plant in question were at risk of certain demise... and a re-pot couldn't wait until spring. Other than that, I'd try to limp along until growth began in early spring.