OK so here is what I have found and what works for me. When free-diving I slowly exhale small amounts of air as I go down to allow me to sink rather than fight the air trapped in my lungs. By the time I reach the depth I intended I now have half the air I originally took in. As I start to run out of air I again exhale small bits. By the time I reach the top I am out of air and my first reaction is to inhale. This immediately feeds my system and reduces the need for "rescue breaths". Practice holding your breath empty rather than full and concentrate on your breathing and your heart rate. Try to slow yourself down as much as possible.
This is possibly the most disturbing freediving "advice" I've see on this board and downright dangerous, setting yourself up for a blackout. The moderator should remove this post.
There is no benefit of exhaling half the air on decent in recreational freediving (advanced FRC diving aside) all you are doing is shortening you bottom time (most people prefer the opposite). The feeling of fullness from a peak inhalation goes away anyway as you descend and the air in your lungs compress. If you are so buoyant that you need to release air to comfortably descend you need more weights.
"As I start to run out of air I again exhale small bits." So you are on the bottom, your oxygen store is now running low and your body tells you to return to the surface and you... exhale(!) which will further reduce your oxygen supply and set yourself up for a blackout before reaching the surface. Also, releasing air at depth will make you less buoyant so now you are kicking up harder expanding even more energy/oxygen to reach the surface.
The exhale in freediving does not occur until 5-6 feet below surface, so we can take that first breath of air the moment we break the surface. We then continue with recovery breathing - NOT "rescue breaths" which is something completely different. If you need "rescue breaths" you have most likely blacked out, you haven't responded to BTT and is hopefully being egressed by a properly trained buddy giving you... "rescue breaths".
"Practice holding your breath empty rather than full and concentrate on your breathing and your heart rate. " - not sure what you have in mind here...
Don't like to jump on other posters but it scares the c--p out me that people new to the sport read nonsense like this and go out and kill themselves.
Get trained and dive safe!
