What would be the best product to paint an aluminium greenhouse, please? It's quite weather-worn. We have cleaned with soapy water and wire brushed to get rid of grime. We prefer a matt finish which is black or anthracite colour. We have sampled Hammerite Ultima Matt Black but are not impressed with the result. It is more of a tinted lacquer with a very streaky finish. Hoping you are able to recommend a suitable product. Many thanks Tracey