Grief - what a nightmare is my first response!
If you are going down the rattle can route, the drawback is I think once you have bought all the necessary items for the job I describe below, you will have spent about £100 - 150; the same as a cheap bodyshop bonnet respray and it is far harder to get a decent job from cans than a gun, simply because the gun delivers paint thicker and wetter with each pass, whereas aerosols deliver thinner and need more coats so more time for something to go wrong.
Whatever you spray on has got to grip a firm paint foundation - a key, the same as if you were painting a front door with gloss; otherwise whatever you spray on will not grip and peel off - back where you started.
So - you need to LIGHTLY sand off any loose clearcoat down to the base (colour) coat - but NO FURTHER, otherwise you will get to the primer and then you will have to drive it to a spray booth or buy a whole load of equipment - see my earlier post. Best way is to wetsand with wet 600 grit wetdry sandpaper and plenty of soap water to keep the area lubricated and prevent the paper from clogging. You will see a white liquid joining the water - that is the clearcoat coming off. If you see red in the sanding water - STOP; you have reached the base colour coat. Wont take long from what I saw in you pic.
Now you have removed the flaky clearcoat and you have got the right key for your paint.
Everything needs to dry off completely and the bonnet/roof needs to be immaculate as far as pits and chips, rust etc are concerned as these will show in the finished job.
Now, you NEED plastic gloves to stop your body oils reacting with the paint as you are bound to touch the bonnet at some point. You NEED a respirator mask and ensure you work with plenty of ventilation. Car paints are flammable - with the amount you are going to use, take the necessary fire precautions. Even a single electric spark can ignite a solvent cloud so BE SAFE.
Wipe off the bonnet with panel wipe and then use a tack rag to lift off any dust just before you start to spray. The cleaner you prep, the better the finished job.
You will need to spray a couple of coats of the base colour coat to hide any scratch marks and discolouration, which there will be as the clearcoat has failed for a while, causing sun-fading. You will need two cans for the bonnet alone. Usually ten minutes between coats to allow solvents to evaporate (flashing). After the final colour coat, wait 30 minutes before clearcoating. Do not sand the colour coats before clearcoating as marks will show through the clear. Spray allowing 50% overlap in your passes to ensure a complete smooth covering. You only need to colour the bonnet - there is no protection in the colour so doesn't need to be thick, just uniformly covered. Please go to a bodyshop supplies shop for your match paint as Halfords or similar wont be anywhere near your car paint even with the car DIN number!
30 mins later ...wipe off with your tack rag ...
Does the colour coat look how you want it to, except it wont shine yet? OK ...
Spray on 4 coats of clearcoat. I can recommend UPOL Clearcoat - easy and very nice to use. You will read on spraying websites that you need to spray 2 coats, but that is with a spray gun which delivers far more paint than aerosols in the same time. 4 coats is far better than 1 or 2 heavy ones. 50% overlap the same and 10 mins between coats.
What you should now have is a coloured and cleared panel. It wont be as tough as a 2K job, but will see you through the life of the car I would think.
There is so much more I haven't mentioned here that you should really research before you go ahead with this project.
I would do these three things first:
1. Put the pic of your car on 101autobody and get loads of advice from a whole bunch of painters from large professional companies down to weekend DIYers. I did, and I am glad I took their collective advice.
2. Drive the car to a bodyshop supplies shop and take their advice. Many of these are sprayers themselves and could point you to a local cheap sprayer who could do a one-off like this for cheaper than you can buy everything you will need.
3. If you are going to DIY, get hold of a scrap panel (or old fridge/washing machine panel etc) and try these methods out so you get a feel for the job before you work on your car. You will be glad you did, better to ruin a scrap panel than your bonnet and make things so bad you have to get professional help.
I ended up buying an air fed mask, compressor and gun and enjoy the confidence this gives me compared to working with aerosols - initially more expensive but loads easier and cheaper in the long run than aerosol. Good luck!
