Temporal ambiguity on mochiko packaging

Question

I am making some shiratama mochi and want to know if I have to scoop the mochi out after they rise, or 1-2 minutes after they rise:

だんごが浮｛う｝きあがって１～２分してから順｛じゅん｝にすくいあげ、冷水｛れいすい｝にとって、さまします。

My first thought was that I am meant to wait until 1-2 minutes after the dango has risen before scooping it into cold water, but the presence of ～てから makes me suspect that the １～２分 is actually an approximation of how long it will take for the dango to rise.

Also, optional bonus question since the は and が differences always challenge me:

Why is が being used instead of は, and would using は instead change anything?

Answer 1

When a series of actions is listed with the verbs in the ～て conjunctive form, the list can parse out to "[VERB], then [VERB], then [VERB]..."

Years ago, a friend of mine at work laughed after getting off the phone with his wife, when he realized that she'd explained her day using almost entirely ～て-form verbs. My memory is fuzzy, but it was something like,

連れて行って話して、帰って食べて寝た。

"With [someone], we went, and talked, then [I? we?] returned home and ate and had a nap."

Here's your sample sentence:

だんごが浮｛う｝きあがって１～２分してから順｛じゅん｝にすくいあげ、冷水｛れいすい｝にとって、さまします。

Let's break this up.

だんごが浮｛う｝きあがって

The dango float up, and then...

１～２分してから

after giving it another 1 to 2 minutes, then...

順｛じゅん｝にすくいあげ、冷水｛れいすい｝にとって、

scooping them out in order (i.e. in the order in which they floated up), put them in cold water, and...

さまします。

cool them off.