How to remove freezer frost?

A steamer such as this one:

Is a commonly used tool since the steam output quickly melts ice but doesn't get hot enough to melt plastic used in the freezer.

I don't have one and have used a handheld blow dryer many times. You need to be careful as it's easy to melt plastic parts and it's also important to avoid water dripping onto or into the blow dryer.

When the tenants leave an iceberg inside the freezer, what I usually do is haul the fridge to the bathroom, put it in the shower, and use the hot water to melt the ice. It works best if the fridge is slightly tilted forward so the water comes out easily. Obviously, one should be very careful not to spray any water on the electrical parts. Let dry fully before plugging it again.

This works best with small fridges that can be easily moved. Since your fridge is huge, instead I'd remove the shelves and tape a rectangular bucket to the back (you can use the drawer for vegetables that comes with the fridge) so water from melted ice drips in the bucket instead of making a puddle on the floor. Then, hair dryer... or you can pour hot water on it.

Note that a freezer that produces a lot of ice means water vapor is getting in, which can mean the tenant put too much stuff in there so the door doesn't close properly, but it can also mean the lip seal around the door has deformed or hardened and it is no longer airtight. In the latter case you should really fix it, because when it's no longer airtight heat and water vapor will get in, and that will make the compressor work harder, which will cost more in electricity. If the seal is really busted, then the temperature inside can get too warm, and you could eat spoiled food too.

Remove all the food, then turn off or unplug the freezer, and prop the door open. This will allow it to warm up and all the ice will melt all by itself.

Every modern fridge/freezer I've ever seen (modern as in 1970s or newer) has a drain hole at the bottom of the compartment and a hose that runs to the drip pan that's behind the trim plate at the bottom of the fridge. Generally a good tug will remove the trim plate, though if yours doesn't come off easily you may want to look for screws.

Remove the trim plate and you'll see the drip pan under there for catching any drips that go down the drains in either compartment. Keep an eye on this catch pan to ensure it doesn't overflow. Soak the water out with some towels that you can ring out over the tub, or scoop it out with a small cup if there's enough room. It's possible that the water will evaporate out nearly as fast as it melts in if your room is warm enough.

Once all the ice is melted out, plug in/turn on the unit, let it get cold, put the food back in.