Found an interesting read from a book by Lee Frost 'Photographer's Guide to Filters' and decided to share some interesting ways of making cheap DIY soft focus filter. Hope it helps (I am still trying the stocking method and love the breathing method)

Summary from the article:

Because of the way soft focus filters work, itís actually very easy to make your own, or to find materials around the home that will create a diffusion effect, so if you donít fancy spending money on the real thing, here are some ideas that you can experiment with.

Breathing on the lens

The easiest and quickest way to create soft focus is simply by breathing on the front element of your lens, or a clear filter placed in front of it. The condensation that forms on the lens or filter adds a misty effect, which is heavy initially, but becomes more subtle as the condensation clears. To make the most of this, watch through your camera viewfinder, and when the effect looks pleasing, take the picture.

Hair Spray

Take an old skylight, UV or warm up filter and spray a very gentle coating of hair spray on it from 20-30cm away. Because the hair spray is tacky, it will stick on the filter and stay there. Allow to dry for a few minutes, then place the filter on your lens to check the effect. If too subtle spray more, if too strong, wash the filter with warm water. Note never spray on the filter when it is mounted to the lens.

Petroleum jelly or Vaseline

Place a tiny blob of petroleum jelly (1-2mm in diameter) on a clear or warm filter, then smear it across the filter surface. Doing this covers the whole filter in a greasy film that degrades the light passing through to produce a very effective form of soft focus. This technique is special in a way because you can vary the effect from one shot to another simply by smearing the jelly in different ways with the finger or a cotton bud. For a delicate soft focus effect you need only a tiny amount of jelly, for more abstract ones, smear more.

Womenís stocking

Hollywood film cameramen devised this simple technique back in the 1940s. All you need to do is to stretch a piece of stocking material over the lens and secure it with a rubber band. The level of diffusion varied by using different grades of stocking material. This is measured in deniers; the smaller the number, the finer the material and the weaker the soft focus effect. Use black stocking for a neutral effect or you could try flesh color ones for a warmer image.

Food Wraps

Sheet of food wrap stretched across the lens will actually produced a delicate form of soft focus. Screwing the wrap into a ball first so that it ceases, then unravel it and stretch it over the camera lens- the crease will enhance the effect it produces.

Hope you guys try it out and see hows the effect