I would caution against any sort of slowed, or skip breathing that you might hear about. You get one good Co2 headache and you will not ever try that again.
Generally being in better cardio fitness, should help you keep a low heart rate and learning to swim and be more efficient in the water will help as well. Although I have seen some weird examples of divers that are very overweight that seem to breath like birds.
Might do a little research on propulsion techniques.
There can be some misunderstanding about what is the purpose of "proper breath control". The main purpose is to avoid CO2 accumulation, not saving air!
"breath control" techniques were developed by military divers during WW2 using the ARO, a CC pure-oxygen, chest-mounted rebreather. As you see here, the first versions were equipped with a single hose:
The scrubber of that rebreather was very poor, as the gas was passing through it back and forth (unlike in modern two-hoses rebreathers). So, for removing CO2, it was necessary to practice an extreme breathing control: very slow, employing completely the lung vital capacity (which means exhaling really all what it is possible to exhale), and practising two pauses, one with all the gas inside the bladder, and one, longer, with all the gas inside your lungs.
The ARO rebreather was widely employed in diving schools here in Italy until 1990, as it was considered very "didactic" before switching to OC Scuba systems.
Going to OC, the expiratory pause is removed, while the inspiratory one is maintained, but reduced to just 4-5 seconds (instead of the 15s recommended when in pure oxygen). Or almost completely removed, but teaching the student employing strongly asymmetrical respiratory cycle, with slow intake and exhaust when the lungs are almost full, and fast exhaust and intake when they are almost empty. This way, for most of the time the exchange surface between blood and gas in your lungs is maximised, improving the capability of removing CO2 from your blood.
Indeed, the respiratory rhythm is still very slow (4 cycles per minute) and using always the full lung vital capacity.
When you learn breathing as above, you will never have CO2 accumulation problems, and your gas consumption will be much smaller than people who were not trained (for months) using it.
However, this approach needed a 9-months-long first level course, which of course is entirely unacceptable for commercial diving agencies, such as PADI or its competitors.
There are also very good reasons for avoiding that people learns this technique, as it can cause other kinds of dangers (but definitely NOT CO2 retention, as it is optimised exactly for avoiding this, maximising the exchange capabilities of the lung surface). These potential dangers are:
1) Lung overpressure and potential barothraumatic emboly if the diver ascend without exhaling, even by just a few feet.
2) As the air consumption is reduced, there is severe risk of prolonging the dive time too much, going well beyond NDL. This is also the reason for which American didactic methods favoured the usage of a single cylinder of limited capacity (typically no more than 12 liters), while traditionally here we were trained using a twin-cylinder of at least 10+10 liters.
In conclusion, commercial training centers suggest to "breath normally" and always avoid to pause your breathing. And there are those two very good safety reasons for teaching this way.
So, before deciding to take the risks connected with learning proper breathing control, evaluate carefully the tradeoff between benefits and added risks.
As an instructor, I changed my approach when switching from teaching in 9-months long courses using mostly the ARO to one-week courses in tropical resorts, starting immediately with an air Scuba system since day one.
In such a short training time it is substantially wrong to teach proper breathing control, the risks do not outweigh the advantages...
And if one student really breaths too much, just give him a larger cylinder. Usually those guys have large shoulders and carry the bigger weight with no problem.
