there are a few ways!

The first way is called MHRT (Magical Hormone Replacement Therapy). Its the same as what we commonly know as HRT but with magical acceleration properties that speed up the process a bit in comparison. its administered through injection and the subject soaks in a magical pool for an hour or so their body can stabilize from the sudden influx of magic into their bodies. It’s also quite relaxing and needs. An added benefit to MHRT is that it improves upon the body by reshaping bone and muscle structures to the masculine or feminine form much more efficiently than our world does. For mtf they will also grow breasts naturally.

MHRT is given to trans ponies after said pony has lived through a certain amount of time as the gender they identify with and, at their discretion, want to take MHRT. MHRT is done once a month until their gender is magically sealed and they can produce the proper hormones naturally (this varies from person to person but can take a minimum of 5 years to achieve.)

The second way, which normally comes after the first, is genital reconstruction and cosmetic surgeries. Which is the same as we know it basically. 

Third, less common and more expensive, is using a geomanced item to warp both others and the user’s perception into perceiving the user’s desired appearance. The wearer has to get them reenchanted every three weeks and cost a pretty penny to do so.

With accessible equestrian healthcare and the fact that Dinky’s family is basically rich/upper-middle class all these options are available to Dinky when/if he decides to go through them. Though the one im rooting for is the first because then Dinky is obligated to take a fucking bath