Pretty much what Connor said. You want to learn to Frenzel. If you have BTV it will come much, much easier, and you should be able to Frenzel hands free with a mask...
For someone with natural BTV, Frenzel is just the BTV you've always done but with a throat lock (closed glottis); if you kept spearing and diving deeper you would probably stumble onto the throat lock part on your own, although to reliably and easily go below residual volume you need to be able to effortlessly maintain the throat lock while opening your etubes, and it gets much harder when you are actually diving with elevated CO2, banging dive response, possible nitrogen narcosis, competition expectations, and several atmospheres of pressure on your chest. From what you describe, you probably are hitting RV around 25M. The mouthfill with tounge piston, relaxed soft palate, and throat lock that you hear so much about will help you equalize your mask once you get below RV, however if you have easy natural BTV the effectiveness of 'frenzel' vs 'mouthfill' when it comes to your ears may be negligable (for non BTV divers the effectiveness of the two techniques seem to differ a lot). If you go over to the darkside and pinch your nose/wear a noseclip traditional mouthfill with tounge piston might buy you extra depth if you can stay relaxed (I usually can't!)
Most of the above is assuming you can open your etubes while maintaining your throat lock; it seems some people who can open their etubes (BTV) can't do so independently of their throat lock and/or soft palate. BTV has always been as easy as blinking for me, although all the other aspects have taken much practice and are an ongoing journey. Currently I can comfortably EQ handsfree, head down in a mask to about 57M. I have done it in glass mask but compressible plastic Sphera is easier.
Also, you may want to practice actually holding the etubes open instead of just clicking them open momentarily. It is difficult but my deepest most comfortable dives to date usually require throat lock+relaxed soft palate+tubes held open, some reverse packing.
