You should not be spraying your buds with anything. You can do foliar feeding, but really you should only do this as a corrective action to stave off issues. I do all of my feedings via top dressing (adding fertilizer to the top of the pot and watering through) and/or teas. Top dressing takes longer to circulate through the plant but is a more gradual feeding, teas react quicker (not as fast as foliar though) and are great particularly if you are growing organic. For chemical feeding, the teas are not as needed since the nutrients are already broken down.
Foliar feeding while you have buds greatly increases the risk of mold, which can destroy your crop. You may be able to do it if you are very careful, I never do.