Depending on what your total system volume is (DT - LR - sandbed [i use 70% of DT as a rough guestimate]) + sump volume) you can plug it into the BRS alkalinity calculator.
Just as a dummy calculation, i plugged you in at 90 gallons of total system volume.
To go from 90 ppm to 150 ppm you need, with the 2 part alkalinity solution from BRS:
216 ml or 7.3 fl oz or 43.2 tsp.
So you're going to be jumping about 60 ppm of alk, OR like 3 dKh. I wouldn't go more than 0.5 dkh or ~9 ppm per day. SO, you're going to divide your dosing up into 7 days of dosing. Each day, dose 43.2 tsp/7 days or ~ 6tsps per day of BRS 2 part alk. I'd dissolve it in maybe 1L of RODI and dose first thing in the morning or whenever your pH low is. To recap: 6 tsps per day for 7 days. Something to consider is that RSCP runs at like 11-12 dKh if you're at 1.025-1.026 salinity. Consequently, your alk may drift up over time. Nothing wrong with that really, just something to be aware of.
Before you dose the first day, check your alk. Test again an hour later to make sure you arent busting like 10 ppm per day of alk increase. Good luck!