The daddy of detergents is TFR (traffic film remover) it can be bought from motor factors. I use it for everything, it strips the crap off tubes and brings them up like new. But, it's prudent to dilute it by at least half and rinse before it drys. Then bear in mind that the gelcoat or whatever you've cleaned is left stripped of all protection. So once dry, polish or tube protector should be applied.
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