I make my own potting soil mix but I allways add a touch of Bone Meal and Dolomite Lime to my soil before potting the plants up.
They both take a while to break down so the plant can use it , so adding it at the time your plant is budding might be too late.
I think it helps with root growth etc. in the early stages of growth and latter with budding.

I use Foli-Cal for buds.
Foli Cal is a concentrate.I buy it in pints (about $9.00) which makes about 10+ gallons of spray.
I add a little every time I fertilize my potted plants.
It's supposed to be a folier spray but I add it to fish emultion and seaweed extract when I fertilise my plants.I spray the soil and plants with the mix.
Blossom set ($6.00 for 8 oz.) is way too expensive but the same thing - basically calcium.