I need some advice on paint spraying, not the whole car just a few touch ups here and there. I have an air compressor and a couple of new unused paint spraying guns to use.
The last time I sprayed a car was 40 years ago and I remember just using cellulose paint. Things have moved on with different types of paint and I need to know what type is easiest and most forgiving for home use? My car is Blenheim silver, a metallic finish.
I have a few small dents to knock out and I will also try my hand at panel beating. Hopefully once the weather turns for the better.
I will start with the slam panel under the bonnet which is not too visible.

Metallic paints are a pain in the ar$e to touch up. You almost inevitably have to paint to a handy shut line unless you're really practiced. Maybe cheaper in the long run to get one of those visiting Dent Magician types to come and do it for you. They have the infrared heaters and the ability to mix the paint to match any fade that has taken place since the car was built.
In addition, modern 2 pack paints require breathing apparatus, water based take an oven or serious sunshine to dry. If you don't seal the original paint it can easily pickle through as well.
If you want to practice I suggest you send your paint code to a company like Autopaints in Brighton:
http://www.autopaintsbrighton.co.uk/
I used to be Brighton based and involved in a chain of garages and we used them all the time.
They'll mix you up an aerosol or two of your paint colour, recommend and supply the type of paint and primer for your purpose, then you can practice on any old body panels you have lying around. Then decide whether you want to go for it on your car.

Autopaints! Now that really takes me back. Didn't they have a place at Lewes too at one time?

They did me a large aerosol and lacquer for a SAAB, Scarab Green semi-metallic, pushing 15 -20 years ago for £ very reasonable which was not only an excellent match but also sprayed very well indeed and covered much better than I expected. Been using it for little odd jobs ever since, just finished it off in November last. OK I don't do much where dark green is a good colour but to keep working after so many years must say something.

Clive