The best non-hold accessory for the Planche: a push-up with a huge forward lean that loads the front delts and biceps tendon exactly like a planche.
Push-up
Cues
Hands low (by the waist), fingers can point out/back, lean shoulders far past the hands, protract (push the floor away). The further forward, the harder.
Programming
3 × 6–10. Pair with planche-lean holds on the skill block.
How to progress
Increase forward lean / hand position lower, then elevate feet. Leverage, not load. → Progression §5