Which technique is commonly used to apply gel nail products?

Layering is commonly used to apply gel nail products because it involves applying multiple thin coats of gel to build up the desired thickness and strength of the nails. This technique allows for a gradual curing process, where each layer is cured under a UV or LED lamp before applying the next. This method ensures that the gel adheres well to the natural nail and creates a durable finish.

Soaking, buffing, and filing serve different purposes in manicure processes. Soaking is typically used to soften the skin or remove old polish, while buffing is a technique for smoothing the nail surface and enhancing shine. Filing is primarily used to shape the nails, not to apply products. Therefore, layering stands out as the essential technique specifically for the application of gel nail products.