I need to redo the putty around the windows in my concrete shed. The last lot (not sure if it was done by my dad or the house's previous owner) was not painted and has started to crack and fall out. I've read it needs overpainting but needs to be an oil based paint. But so many of the paints like the ronseal ones all seem to be water based. I only need a tiny amount just to go round the putty on 3 windows - can anyone suggest where you can find small tins of oil based exterior paint (do screwfix do any as I could only find water based or a few large cans of oil based), is there a specific one I need to get, do I need to use a primer too, or are there any other, preferably more environmentally friendly, alternatives to treat the putty instead of oil based paint?