I just had my Bertram 20 hull done using the Farrow process.
It had lots (years...) of bottom paint on it. Blaster actually though it might have been epoxy barrier coated in the past, because he came upon some hard grey material. He had started to only work down to this layer, but broke through and found more bottom paint. In reality, some poor sap had paid for a barrier job but only had some epoxy slapped on top of the old bottom paint.
I had it done and it was $480 earlier this summer.
Ian.