Got a mobile home I'm trying to help with. Where the evaporator coil is held is a problem. It's in an area with the hot water heater which is typical for this home plan but that area is very dirty and it seems someone modified the area.

I need to know the best way to clean this without removing the coil. Can I hit it with any pressure or what is the best course?

What should I do about the closet space this unit sits in? Should I try to enclose it better? And there isnt a place for a filter so please suggest how to remedy this. Photos below

 

Here are the photos of the AC unit

 

That filter laying against the coil will not work.
Moisture that normally covers the coil surface will turn it into a muddy mess.

The grill above the furnace door is meant to hold the air filter.
it is normally a piece of coarse fibre cut to fit the space and some type of spring or strap to hold it in place.
A large fibreglass filter could be taped or secured to the inside surface as well.

To help clean the coil you could first use a stiff brush and stroke with the direction of the fins to remove the surface dirt.
Sometimes those waterless coil cleaners will remove alot of the embeded dirt, helped along with a spray bottle of water.