Using the brett yeast is what takes the time, and a good portion of what makes it a Lambic. If you don't want to do the time, don't do the yeast.
I used 6-6# fresh raspberries in secondary and it was beautiful. I don't know how that turns into cans of puree, but I imagine it would be similar.
I would also consider using acidulated malt to bring a little of the sourness into the brew.
Copied from BrewBoard's "Impatient Man's Lambic-ish":
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....THE IMPATIENT MAN'S LAMBIC-ISH FRAMBOISE....
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........................... "A Cheater's Framboise" ........................
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(Calculations are for 5.5 gallons, assuming .5 gallons lost to trub in the kettle, etc. I boiled 5.5 gal's and topped off to remake volume before chilling)
GRAINS
Mash:
7.5 lb British two-row
0.6 lb Crystal 20L
0.6 lb Crystal 40L
0.6 lb British crystal 50-60L
0.25 lb CaraPils
1 oz Black Patent
1 oz Roasted Barley
1/2 oz Smoked Malt
(Gravity at this point is 1.044)
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SOURING THE WORT
Add 1/2 lb crushed (but unmashed) 2-Row malt to the wort/runnings once it has cooled to 120 degrees F
Let it sit for 15-24 hours, insulated with a blanket.
Important:
Keep close tabs on it in the hours after 12. As with all things bacterial, and fungal, I think the activity was exponential. It soured a LOT in the last few hours. Keep an eye on it when doing this, esp. in the later hours and don't "assume" a certain amount time will be right. Ii got very very sour in the last 3 hours, when it had seemingly not soured at all (at least to taste) in the first 12 hours).
Also:
Pitch in the ground unmashed grains at about 120 degrees into the wort, not 130, as Papazian mentions. The higher temp seems to pasteurize or shock the stinky lactobacillus / pedococcus / diaperbacillus bugs. 110-120 works fine.
Also:
I kept the wort in my kettle as it was souring. I did not want to possibly infect anything in my brew-works with the lacto-bugs. I figured the boil would eventually kill everything in the kettle off.
Oh:
It will taste absolutely awful when it is done souring: sour, and "funky/moldy"
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THE BOIL
Skim any gunk that has formed on top of the wort. Then pour the wort off of the crud (from the unmashed grains) at bottom of whatever vessel you soured it in, and put back in your kettle.
Bring the Wort to a boil.
(Total boil time is 90 minutes)
Boil for 30 minutes. It will stink like hell for the first 30 minutes of the boil...
At 30 minutes into the boil
HOPS
60 Minutes: 0.25 oz Stale Cascade hops 5.3%* (plug)
30 Minutes: 0.25 oz Stale Cascade hops 5.3%* (plug)
* These were old and very stale, so they had little or no bittering properties-- so the AA's there are probably not realistic AT ALL. I recently read you could do that to your hops by drying them out in a low oven for a while
15 minutes:
Add to the boil 1lb Wheat DME
(Recipe gravity before wheat: 44. With Wheat Extract 51.)
Whirlfloc @ 10 minutes.
Flameout.
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PRIMARY FERMENTATION
Top off with water to reach 5.5 gallons, Cool, and rack into primary fermenter.
Pitch a healthy starter of American Ale Yeast 2 (Wyeast # 1272), and wait for hell to break loose. This one ferments wildly, and with the wheat dme, a blowoff tube is an absolute necessity.
A note on my yeast choice: I chose this because of its description: "Fruitier and more flocculant than 1056, slightly nutty, soft, clean, slightly tart finish." Fruity and tart is what I was looking for, along with the "unplaceable" nuttiness. I also wanted a kick-butt strong-fermenting yeast with good attenuation. All seemed to fit the bill with 1272. I fermented at the top of it's range (72 degrees) to accentuate the fruity aspects of it. I am sure you could use a Belgian yeast if you wanted to, but the reason I used this one is because of the impatience.
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SECONDARY FERMENTATION (& the Framboise part)
When primary fermentation is pretty much done (5 days or so), rack the wort into a 6.5 gal secondary (transferring some of the highly flocculant yeast), on top of:
8-9 lbs of Raspberries
I used frozen raspberries which were added to a pint of water (to prevent scorching/pectin setting on the stove), and pasteurized at 140 degrees for 25 mins and then cooled.
Now wait for hell to REALLY break loose. Attach a blowoff tube. Trust me.
When fermentation settles down, add pectic enzyme (at slightly higher doses than normal because of the alcohol content of the fermenter).
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TERTIARY FERMENTATION
Rack (avoiding the raspberry gunk) to a Tertiary fermenter to clear when secondary is done.
(OPTIONAL: Depending on how sweet you want this to be, add up to 3 lbs (yes, 3 lbs) Lactose (boiled in enough water to dissolve it). I added most of it, but if you want something very dry, add none. It will be very, very dry, eventually.)
Let settle/ferment/condition/clarify/whatever for about 2 weeks. For some reason, despite gravity readings being steady, I still got bubbling in my pipe. When I tasted it, it had a lot of CO2 in solution, which I think is what is bubbling).
My final gravity was in the neighborhood of 1.010-1.012
Bottle with a healthy dose of carbonation (more than normal; suggest 5 oz corn sugar or, in my case, 3/4 cup honey).
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