Sulfur is the "secret" ingredient in Bloom boosters to pump up the trichs. I'm experimenting with adding some MSM, methylsulphonylmethane, to see if it has an effect on resin production. I bought a pound of it to make caps for my arthritis and thought I would try it out on the plants. I have 5 identical clones at 40 days flower so I'll just dose 1 and see what happens. 1 was dosed heavy with Bud Ignitor and there is no noticeable difference in it's buds compared the the others nor did flowers form faster as advertised so I won't waste anymore money on that stuff.
Big Bud has 10% S and is used early in flowering so Im not sure you have to wait until near the end. I won't grow without it and have used it since Dr. Hornsby first invented it.