Decoction?? Q's

So I watched the Youtube videos on decoction and tried it last night, two thing I would like to ask:

1. on the calculation for decoction volume, Kaiser worked on 19L, but also said +/- 3 L water per 1kg of malt (which would then be 12 L)?

2. Do you then sparge with water after aswell? or is it no sparge?

So I also used 4 kg malt, and stole KAISERS volumes for enhanced Double Decoction, from the video ,and had a bit of a problem reaching temps. I think the mash was to thin/large and I live high above sea level thus boil temp is actualy @ 95.C (only realized it half way in)

Decoction is method for increasing temperature to hit specific rest temperatures in a mash. If you use decoctions, you would sparge at the end of the mash as normal.

I always pull about 30% more decoction than I think I'll need, in case I don't hit my target temperature. If you hit the target and have some boiled decoction left over, just let it fall in temperature and then add to the mash when the temps are equal.