Forearm balance is deceptively challenge, and not for the reason you may think. The "going upside down" part of the pose is significantly easier for most students than handstand; the tricky part is developing strong enough rotator-cuff stability before you get to the upside down part so you don't face plant while trying to get up. (Got to got to get up to get down. Ha.)
Find your forearm balance weak points.
Sitting on your knees, try setting up your arms overhead as if you were going into headstand, and then separate your forearms as if you were in forearm balance - wrists out to align, elbows stay forward. Can't tell if you're aligned? Take one hand and place it on your elbow, and then as you draw your upper arm closer to your head and your elbow forward, bring your wrist in line with your elbow.
You could strengthen here by contracting and relaxing your muscles, pressing your elbow into your palm and then switching sides (press in and press out all while keeping your arm in this position).
Take it the floor. Or the wall.
You can use a block here (if you use the wall, watch your head doesn't get bonked by the block!) and then align your forearms by measuring hand-to-bicep and releasing, set up dolphin with the L shape of your index finger and thumb around the edges of the block. Press your forearms down and try to shred your mat apart (press down and apart) while wrapping your shoulders away from your neck and up toward your waist. Then try to squeeze the block into nothing by pressing your forearms down and toward one another. (Nothing actually moves, we're just building strength.)
Keep your spine long, ribs toward your hips, upper legs strong.
Forearm balance/pincha mayurasana with the wall.
Set up with your block near the wall and get into dolphin pose. Look forward - get your shoulder wrap - press your forearms down. Lean forward (it's weird, and do it anyway) and lift one leg up to the wall. Lift both legs to the wall. Try internally rotating your leg toward your centre line. Toes spread. Feet strong.
Eccentrically train out of forearm balance.
Try to keep one leg on the wall, and lower your other leg toward the mat as if it were super s l o w l y reaching down. Land gracefully. Switch sides and do the other leg. Do this many, many times for months.
Get off the wall.
Take your block with you, set it up in your hand-L's. Look forward - get your shoulder wrap - strong spacious toes - learn forward toward your hands - and lift your leg. Bounce lightly on the opposite leg to lift it up, too. Find halfway between "shredding" and compressing your forearms and keep lifting up. STRONG SPACIOUS TOES REACHING UP!
Get off the wall without a block.
Follow the same directions as with the block, but don't use it! If you try this, and you're afraid, come closer to the wall so that if you tumble, you can bounce off the wall and land back in dolphin. The park is also a good place to practice (bring your block!)
If your arms are still tracking hands-in-elbows-out, keep practicing with the block.
Strong, stable shoulders are such a joy to have. Less injury, greater freedom, greater confidence, ease and flow through the upper chakras. Both dolphin and pincha mayurasana are phenomenal poses to practice for these reasons!
Got questions about forearm balance/pincha mayurasana? I'm happy to answer them! x