stepping up to a 10g batch

is it the same as doing a 6g batch?

1.25quarts x pounds of grain= strike volume

then after, sparge with 10gallons of sparge water at 175F(split into however many times my mashtun will hold)?

Yep, same procedure. I like to think of it as sparging to reach your desired preboil volume. But a 10 gal sparge plus first runnings should give you 11-12 gallons in the kettle

If you have a 10 gallon mash tun, you will get by with 2 sparges, on my system I get close to 14 gallons with first runings and a 10 gallon sparge, moving up to a 10 gallon batch is the way to go, you get so much more beer for almost the same amount of time, I just got a 24.5 gallon kettle and will be moving up to at least 18 gallon batches, Ill work up from there, I have to see how much boil volume I can get by with, good luck, and brew on.