Starting first partial mash tomorrow

I transferred my first beer into my secondary this past weekend, using my brother's Mr. Beer kit that I modified by adding a real airlock to the lid. I know the Pale Ale didn't need a secondary but I needed to free up my Better Bottle for another small brew...the Ale Pail is reserved for a 5 gallon batch of a La Fin du Monde clone that I'm starting soon.

Going to try making a Brown Ale with a partial mash using DeathBrewer's procedure. Wanted to start today but still have to work out some math and I don't have enough time before work (stupid closing shift on a holiday). I thought I had everything I needed except when I checked out the grain bag I bought at my LHBS it's too small. It will hold a lot except it's long and narrow. I've been reading that people use paint strainer bags so I checked out the Lowe's website to see what I could get and this is what they have:
http://www.lowes.com/pd_126392-968-11581/12FF_0__?productId=1008385&Ntt=paint+strainer&pl=1&currentURL=%2Fpl__0__s%3FNtt%3Dpaint%2Bstrainer&facetInfo=
Would that work? It's not nylon, the description says plastic. If that doesn't work I'll pick up some cheesecloth at Walmart instead when I grab the water.

Here's the recipe I'll be using for a 2.5 gallon batch along with mash calculations, someone please let me know if I have them right or wrong.

Brown Ale - Partial Mash - 2.5 gallon batch
1 lb 6 oz Briess 2-Row Brewer's Malt
4 oz Briess Crystal 60L
4 oz Briess 6-Row Chocolate Malt
2 lbs Briess Golden Light DME

.5 oz Cluster @ 7.9% AA - 60 Minutes
.25 oz East Kent Goldings @ 4.5% AA - 15 Minutes
.5 tsp Irish Moss - 15 Minutes

Safale US-04 English Ale Yeast

From what I've been reading I'm looking at using a mash thickness of 1.25 qt/lb. That would be 2.34 qt of water. If I go down to 2.25 qt which is easier to measure I'd get 1.2 qt/lb which is close enough. Using some calculators I'd need a strike temp of ~166* to drop to ~150* after adding the grains. The recipe I'm basing this off of (only change is the hops, doubling the Chocolate malt, and using DME instead of LME) says to mash at 150* for 90 minutes. Now the sparge water should be around 170* but I'm iffy on the amount. I read somewhere to use 2 qts per lb of grain so that would be 3.75 qts...does that sound right? After mash/sparge top off boil pot to a 3 gallon boil size.

Going to leave this in the primary with an ambient temp of ~62* for 3-4 weeks before bottling.

Please let me know if this is correct or what corrections need to be made.

I was roaming the unanswered threads and came across yours. Did you already brew? If yes, well consider what I say for future brews.

Your question regarding the paint strainer; I am not too familiar if that paint straining bag would work. The ones I buy at home depot say nylon. I would give it a go though. Always remember to boil new bags for a couple of minutes before using them, this way you will not introduce that new stuff smell to the wort.

When I did mini mash batches, I would use about 1.5 times more water than my strike water.

62 sounds like a good “ambient temperature” to ferment at, but that is all relative to the fermentation at hand. I notice different yeast produce more heat when they eat. You should really be concerned with the temperature of the beer inside the fermentor. Sometimes that can range from 3 to 10 degrees more than what ambient temperature is. Get a little sticky thermometer from the pet store and slap it on the side of your carboy or bucket.