There's a bunch of different methods to casting boolits. Or three main methods with variations.
1. Ladle casting.
2. Bottom pouring.
3. Pressure casting.
Ladle casting is simply pouring molten alloy on top of the sprue plate, attempting to hit the hole in the sprue plate.
Bottom pouring is similar to flooding the sprue plate with alloy, BUT the thin narrow stream can be aimed to enter the sprue hole directly in the center. This is done by the use of mold guides that position the sprue hole under the spout.
Pressure casting is accomplished by several related methods. A ladle like the rowel, or Lyman has a teet or spout on the bottom of the bowl. It's shaped like the chamfer of the sprue hole, to mate with it to create a seal. The teet is seated in that chamfered hole, then the ladle and mold is rotated to the verticle to let the lead flow into the mold. The ladle is held in contact with the sprue plat for a few seconds, which allows the cooling boolit to draw lead alloy from the bowl of the ladle. That the ladle is separated from the sprue plate to form a sprue puddle.
Bottom pouring is much faster than ladle casting. Some will argue it just as fast, but I disagree. Especially when casting with more than a 2 cavity mold.
Another thing is where the lead alloy is coming from. Ladles have to be dipped into the surface of the lead, DUH! That agitates the hot lead causing it to oxidize more rapidly. ANY disturbance of the surface of the alloy introduces it to the atmospheric oxygen, causing oxides to form. Oxides that get included,(inclusions), will cause lighter boolits and surface defects.
Bottom pour pots, and ladles that pour from under the surface of the molten lead alloy, prevent those inclusions.
Lead alloy needs to be fluxed to re-combine the oxides with the alloy. Any carbon bearing substance can be used. The best is sawdust, put it in until it it chars then stir the alloy to remove the dirt and return the oxides to the melt.
I use a combination of the Lyman ladle and the lee 20# bottom pour pot. I also have a lee 20# melter that I use when I'm making a bunch of big boolits. I have at least 10 lee six cavity molds that all get bottom poured. They're mainly handgun boolits. The others are 2 and 4 cavities, some are bottom poured, the rest are pressure cast. I do NOT flood pour from a ladle, too big of a mess! Some of my Mihec molds cannot be flood cast. The rods that support the HP pins would be impossible to use if lead got dumped on them.
The guide rods are on the back side of this mold. They consist of thin steel pins with "E" clips on them, they would be held from sliding if lead got dumped on them. This is a fine example of a cramer type HP mold.