The Slade School syllabus of Stanley's day provided under Henry Tonks a solid grounding in drawing and composition, but gave less emphasis to the techniques of painting. Although Stanley frequently complained of this gap in his training, it did not prevent him as a twenty-one year old from painting his superb Self Portrait of 1913/14, in every way as accomplished as that of the young Turner or of the nineteen-year-old Samuel Palmer. Moreover, his brother Sydney wrote at the time in his diary, he has done it all with penny brushes!

One effect of Stanley's relative lack of painting instruction was that he had to overcome the more difficult problems by trial-and-error, and was always delighted when he felt he had achieved a result comparable to that of the great masters. Ian Kellam as a young music student in the later 1950s used to visit him at his Cookham cottage, and remembers being called upstairs on one occasion to the front bedroom Stanley used as a studio to be excitedly shown the success with which he had painted the ripples round the swans in his then current Christ Preaching at Cookham Regatta.

Two other successes Stanley records in his memoirs are the wet sponge in the Burghclere panel Ablutions, for which he borrowed his wife Hilda's bath sponge, and the fur robes in his portrait of Jack Martineau as Master of the Guild of Brewers. Stanley took the trouble to visit the National Gallery to see how his fur compared, and came away convinced that his was as good as Titian's.

His magnificent portrait of his first wife Hilda called Hilda and Unity with Dolls,1937, and the astonishing nudes of his second wife Patricia also done in the 1930s (and so distinct in character from his other work) yield to no painter in their technical accomplishment.

Later, in the 1950s, Stanley began to feel the onset of mortality. Desperate to complete as many as he could of his visionary paintings at a time when he was under pressure from his dealer Tooth to fulfil the commissions for landscapes and portraits which his celebrity had attracted, he began to thin the paint on his visionary work, enabling it to dry quickly and allowing him to work on it at short notice. These thinner colours,
sometimes applied so lightly that the underlying pencil composition shows through, have been labelled his boiled sweet colours, and have become the subject of some artistic criticism in the academic sense. But for Stanley, it was more important to use the time left him to convey the 'messages' of his great paintings than it was to comply with scholastic criteria. In any case, it is a matter of dispute as to whether these ‘boiled sweet’ colours did necessarily diminish his presentation. They can, for example, be said to lighten the mood of Christ Preaching at Cookham Regatta to convey the sense of universal happiness he wanted the picture to express.