I use my bk as an hlt.
I heat up my mash water in my mash tun (keggle), and at about 160F, I stir in my grain.
When it gets about 20 minutes from sparge time, I heat up my sparge water in my hlt.
When the mash is done, I drain my initial mash to a cooler.
Then, I move my sparge water into the mash tun for the sparge.
That leaves the hlt open, so I move the wort from the cooler to the bk/hlt, and start heating it up.
When the sparge is done, I drain that into the bk, in which the first run of wort is starting to boil by then.
After that, I do the boil, cool, and get it into the fermenter.