Hmm, 4-6lb would be a flat cut, probably labeled as
center cut. It will be trimmed lean, so may need a few tricks to keep it moist while it takes a long, slow ride to get tender...it's do-able, though. Wally-world or Sam's and other big-box stores regularly carry them. Whole packers are $4.59'lb around here now...trimmed flats would be at least that plus a buck or so, but our meat prices are usually higher than most places.
Time could run about that, but could be less as well. Trimmed flats have a lower cross-sectional density, meaning not as thick as a whole packer, especially if un-trimmed. I checked back and see you have a Master Forge propane smoker...not familiar with it's convection efficiency, but it could be very similar to my Smoke Vault, in that respect.
For a trimmed flat or center-cut, I would run around 215-220* smoke chamber temp, and start with a wet water pan for better smoke reaction. Probe for internal temps after about 4 hours and dump the water after reaching 150*+ I/T. Wait, scratch the water pan...clean-up your water pan good and add washed pea gravel or play sand (season this by heating up for 20-30 minutes over medium flame...the sand/gravel acts as a thermal mass for better control of temp swings). When you're ready to smoke, put a foil drippings catch over the water pan, just on top of the gravel or sand. Have a lip on the foil drip catch so you can add 1/2 qt or so of water. A small baking pan would also work for this as long as it doesn't baffle the heat (is not larger than the water pan's foot-print). The water will evaporate more slowly than it would if it were directly in the pan and will aid in smoke reaction. If the water is gone after 4-5 hours, leave it dry. The drier smoke chamber will seal-up the meat's surface and reduce natural moisture evaporation from the meat by tightening the meat's fibers. Works like a charm in keeping leaner cuts moist when finished at higher internal temps. I've done quite a few posts on this method already, and the results have been very convincing. It does develop a bark on the meat as well (can be very pronounced), though if you don't want bark, you can rest foiled and it will soften the bark during resting from it's own steam in the foil. I use this method strictly for no-foiled smokes, and use it for all my hot smokes, lately.
Wet to dry smoke chamber has been my "go to" method for many smokes since last spring, and I find it very effective for achieving moist meats. I just haven't had the opportunity to use this method with a lean trimmed brisket (yet...clock is ticking, though). Let me know if this sounds like something you'd be interested in trying, or would like to know more about it. It is a snap to make it work with vertical smokers, btw, and I've used it with a highly modified Brinkmann Gourmet charcoal as well as my Smoke Vault 24 gasser.
Here's a few threads that may open up your mind to the possibilities for a lean-trimmed brisket flat and what the wet/dry smoke chamber method can do for it, among other meats (listed from most recent to oldest):
http://www.smokingmeatforums.com/t/...chamber-cherry-rbp-rub-recipe-q-view-finished
http://www.smokingmeatforums.com/t/...hamber-cherry-balsamic-finishing-sauce-q-view
http://www.smokingmeatforums.com/t/127603/16lbs-lbrs-idahoes-beans-dry-smoke-chamber-q-view
http://www.smokingmeatforums.com/t/...-wet-dry-smoke-chamber-humidity-q-view-method
http://www.smokingmeatforums.com/t/...mmed-butt-wet-dry-smoke-chamber-q-view-method
http://www.smokingmeatforums.com/t/...n-gourmet-w-dry-smoke-chamber-q-view-finished
I don't mean to give you an information overload here...just want you to have a very good 1st brisket experience and a fine meal for your efforts. And, there are many ways to pull together the finish of a brisket with Au Jus (Chef JimmyJ, jarjarchef and a few others here have posts on this, if I recall correctly), or the base for a light finishing sauce. A good brisket doesn't need much to bring it all home, though, and Au Jus is one of the best, most simple ways to do it. The natural drippings from the meat (caught in the drippings catch over the dry water pan, for example) is the best way to start a great smoked beef finish on the plate.
Keep in touch...this thread's got me wanting to try a brisket flat again (haven't smoked brisket since early last spring), only now I'm armed with a better smoke chamber humidity control method (wet/dry) from other meats I've smoked. I'd love to hear of you trying it to confirm it for me, as I won't have the opportunity for several weeks yet, as my work schedule has been an overload, and my next smoke will be a ribs & rib eye (from a 7-bone whole beef rib) for Christmas dinner (will use wet/dry chamber for this as well). I have no doubts it will yield moist and tender brisket.
Looking forward to hearing back from you!
Eric
