You're in luck timbo! You don't really need them if you go down the MaxiBIAB path, you'll find that it is largely independent of volume and temperature calculators etc, here are my tips:
For a 19L pot 4.5kg seems about right for 20- 23L of 1.050 OG, if you're using a bigger kettle then it should be easy peasy. Give that a go and adjust total grain bill up or down to suit your desired OG for each batch and for your particular efficiency (should be mid- 70s).
Overheat the strike water, place insulation on and allow everything to heat up and stabilize, let it return to your target mash temperature + 5C.
You want to mash with the kettle full, when starting though fill the kettle to about 3/4 maybe a little more. Once you've preheated the insulation (as above), reserve a few litres in a jug, mash in, fill to the top with either cold, reserved or hot to exactly the temperature you require. This helps makes it quite calculator- independent.
Don't touch it during the mash, particularly early on as all you'll do is lose precious heat, only lift the lid at 60 minutes and give it a stir, let it rest for another 30. Don't mashout in- situ, the sparge does that.
Sparge with 6-8L near- boiling water (nb. don't sparge with liquor- use plain water!), acidified will help but not mandatory. Repeat with 2-4L if the first sparge runnings are still really high, SG should be around half of the first runnings.
You want the kettle as full as possible at the end of the boil but don't add any more sparge in the last 15 minutes, that will ensure it is all sanitary.
Independence from any particular brewing application is one of the features of MaxiBIAB, by all means use it to sort the recipe out to your specifications but after that it is not required, most of them struggle with MaxiBIAB anyway. Obviously, single infusion is the simplest, whereas decoction or multiple infusion will be harder, but single is a great place to find your feet and make fantastic beers.
The
MaxiBIAB guide doesn't need downloading, its just images in a forum thread?
