Jase, unfortunately it's not all that simple. There is a lot of information out there and much of it not all that helpful. The 5.2 product may be a magic bullet but I've never used it so I can't offer any advice there.
OldBugman has sent you down the right path - chapter 15 in How to Brew is really the best treatise on mash pH going around. Almost every book on brewing misses the concept that Palmer talks about - residual alkalinity. All the other books mess around too much with matching water profiles - this is generally a bum steer.
The basic principle is to get your mash pH to between 5.4 and 5.7 (when measured at room temperature). This ensures the right conditions for the mash enzymes and the correct pH for the finished beer. You need to do this during the mash, not afterwards as you mentioned.
The main two factors affecting your mash pH are the various ion levels in your water and the colour of your mash - determined by the amount of dark grains. Compounds in the grains combine with the ions in the water and determine your mash pH. In general, darker grains lower pH, calcium ions lower pH and carbonates raise pH. Other ions, like sodium and sulphates, change the flavour of your beer.
I find, with my water chemistry, that I can use a bit of gypsum or lactic acid to lower pH in pale beers, and a bit of sodium bicarbonate to raise pH in very dark beers. Amber coloured beers are the sweet spot for my water - I don't need to adjust with them.
The best resources I found are:
- Palmer's chapter 15 -
http://howtobrew.com/section3/chapter15.html
- Noonan's "New Brewing Lager Beers" - although he completely misses the critical "residual alkalinity" concept it covers general brewing water chemistry very well.
- Two episodes of the "Basic Brewing Radio" podcast - the episodes "pH with John Palmer" and "Water with Greg Noonan". Both are full of solid practical advice.
- The "Water Chemistry Spreadsheet" on this page:
http://www.antiochsudsuckers.com/tom/ - I find it gives better figures than Palmer's spreadsheet - it's only deficiency is that it doesn't list sodium bicarb as a possible addition.
- Search here (or the web) on "residual alkalinity". Be wary of blindly attempting to match famous water profiles.
The best advice I heard on water chemistry was in one of the podcasts I mentioned - don't mess around with your water chemistry unless you are sure you have a problem with it.
