I typically employ a modified no-sparge method simply b/c I prefer how my system handles it better. I use Palmer's How to Brew calculations on his No-sparge calcs "the long way" which really isn't that complicated or long.

I still use a 1.5 qt/# mash ratio for the scaled up grains (this is also based on the size of the OG and my mash tun capability) after calculating the scale up factor using Palmers math. Then I use his mash-out water calculation to determine the amount of water I need to add to the mash tun to reach a typical mash out temp of around 168-170F (usually heated to around 200F based on initial conversion temps used). I add that water after 60-90 minutes of conversion rest based on my mash temps, then run the mash out for about 10-15 min. After that, its on to vorlaufing and draining the whole wort amount into the kettle for boiling.