My best sessions with similar white teas usually start with about 1 gram of leaf per 30 mL water, so about 2 grams for a gaiwan that holds 60 mL comfortably. Then water about 160 degrees to start, first infusion 1-2 minutes, 2nd similar but a little longer, then up the temp, depending on the tea, to 170 or 180 for another 1-3 infusions at increasing lengths, until the flavor runs out and I get sweet water, or the infusions become unpleasant due to some escaping astringency or bitterness.
I also enjoy quite a few nice white teas as cold-brewed tea, for 3-4 hours up to overnight. I don't usually measure the proportions carefully enough there to give details. Just tea, cold tap water, and refrigerate until ready to drain & drink. A nice Pai Mu Tan is lovely brewed this way.