Never did Billboards Don, but did do some giant formula Ford and Go-Cart photo's for a local garage, together with some Head and Shoulders Hair Style shots for a couple of local Hairdressers, both in colour and B&W. Home made print tanks were sections of 6 inch drain pipes, cut to size and capped placed on some steadily turning rollers,geared down and turned by an electric motor. Very Heath Robinson - but worked. Problem was that sometimes exposures of paper ( used enlarger horizontally and projected onto wall) could be 40 minutes plus - That was in the days when I did things just to see if I could