I really wouldn't recommend furniture polish - it has alsorts of chemicals in that are harmful to horses! Instead, use a mix of baby oil and water :)
While you can add veggie oil to feed, it will not do the same job as cod liver oil. Unless your horse needs cod liver oil, then don't feed it! A splash of veggie oil will give shine to the coat :)
Here are my tips:
Use a mix of 1 part tea tree oil, 1 part citronella oil and 4 parts water as a fly repellent (spray bottles available from Tesco for about £1)
Use Dettoll, mixed to the concentration for treating cuts and grazes, to deter flies and treat wounds on sweet itch sufferers.
Instead of soaking hay in gallons of cold water, (which we all know = cold wet jods!) put the hay in a rubbish bin (a clean one of course) and add one or two kettle-fulls of boiled water. Replace the lid and leave to steam for half an hour.
Instead of buying expensive creams to treat cuts and grazes, I use zinc and castor oil cream (aka Sudocrem or nappy rash cream!) - great for those with mud fever as a barrier
On the advice of my vet, I supplement one of my horses (who gets mud fever at the thought of entering a muddy field) with Zinc (from Tesco!) and within literally a week, his mud fever had gone. I feed 4 tablets (60mg for a 550Kg horse).
Use a fleece/summer sheet as a base rug through winter - wash it weekly and it'll keep the lining of your thick stable rugs cleaner for longer. you can was a summer sheet in your machine, saving money on cleaning bills.
I know people who use nappies as poultices too, in place of animalintex. Personally I've never tried it but I don't see why it wouldn't work.
Baby oil and water in a spray bottle is a great mane and tail conditioner
Make treats using porridge oats (make sure they are just oats, not added sugar etc), add a little water and grated carrot/apple etc. Add a little bit of egg to bind the mixture together and bake in the oven! Remember that everything adds up so don't give these too often - one or two a day is sufficient.
ADD: Ooh also:
a mix of 1 part iodine to 4 parts linseed oil for feet - promotes health and elasticity.
Not sure about Jeyes Fluid for thrush...sounds a bit cruel to me (have you ever spilled Jeyes Fluid on yourself, agony). Instead treat thrush with liquid peroxide. It kills the bacteria by making the conditions inhospitable to them. Just a splash is enough. This is good for gravel too.