UKPassats

Recently my wife inherited a rather nice, and I must add, very quick LHD Passat GT. Although having sound mechanics and interior the paintwork is very dull. We have decided to clean it up and let my son use it. Now I don’t feel very confident about going down the clay bar route, fearing I might do more damage, what would you recommend as the best DIY route to recovering the shine? As the car has cost nothing I don’t mind spending a little on polish etc. what’s the best to get!! Also I don't have access to a DA or mop. What works well on Nappa Leather for fine cracks too . Thanks.