The most obvious reason for cleaning house plants is to remove dust from the leaves and improve their appearance. However, it's also worth considering how cleaning can improve photosynthesis, keep pores unblocked so a plant can breathe and prevent pests or disease problems.
Photosynthesis (the process of plants converting light energy into chemical energy) occurs through light, so it makes sense when a plant is covered with dust that it will receive less sunlight, restricting growth. Cleaning can also help keep insects at bay, help you spot a possible infestation or remove the pests.
The most common method for cleaning house plant leaves is to use a damp clean sponge or soft cloth. This method is usually used on the foliage plants with larger leaves and without hairs. A rubber plant, cast iron, peace lily, bromeliads and many others can be cleaned this way.
First clean the leaves with a dry cloth or sponge to remove as much dust as possible. Otherwise you can end up creating clumps of dirt when the dust gathers together with water. You could even dust them with a brush as mentioned below first. After dusting - use the wet cloth or sponge gently while keeping your hand at the back of the leaf for support.
Using a soft brush is the best way of cleaning when the leaves are hairy. Any type of small brush will suffice if it has soft bristles. I use a small paint brush. African violets, succulents and cacti are among plants which should be brushed.
Many plants with thin leaves such as ferns, palms and others will respond well to being sprayed, like you would when misting a plant to improve humidity levels.
I would advise you to remove as much dust as possible with a brush to prevent dirt gathering and getting clogged up in the crowns.
During the summer when it's warm enough and raining - you have a great opportunity to give your plants a thorough clean by placing them outdoors.
The added benefit of placing them outside during a downpour is the rain will flush the soil of salts and you will be providing them with the best water you could give.
Don't do this with a new plant. It's already trying to acclimatize and moving it again could cause problems.
When the rain stops make sure plants are not sitting in direct sunlight (leaves will get scorched) and bring them back indoors.
Making leaves shiny is purely about making a plant look more attractive and not about a plants health. This can cause other problems which depends on what your using to make them shine.
There are products sold and all sorts of mixtures made up by others to create a good shine. However, it concerns me that many products can cause the leaf pores to become blocked and can attract more dust. Some ingredients used that are sweet could also attract insects.
If you do try a method or product to produce a shine then you might want to test what your using out on one leaf first to see if it works and how the leaf reacts.