The mini has had new floor and inner/outer sills fitted and various other repairs to heel board, boot floor corners and rear valance and closing panel replacement too.
Majority of panels are Heritage except for a few M-Machine repair panels (which were bare metal) and some made from sheet.
Now I want to stone chip the underside with Gravitex but am unsure of the necessary prep needed before doing this, I've looked on here and elsewhere and there seem to be too many conflicting opinions on what is correct/best to do?
Most of the area to be covered is the black coating that Heritage spray their panels with.
Some areas where bare metal was used or a weld joint is have been sprayed with a primer to stop rust starting too quickly before prep.
Some ares are original (boot floor wheel tray, tunnel and parts of wheel arches) and need cleaning back to remove old underseal and surface rust.
My question is this: Once the 'original' areas are stripped back, is there a specific product that's good to paint over the WHOLE underside before applying the stone chip or do I need to use a rust encapsulator/red oxide type product on the bare metal only and THEN an overall paint of something like epoxy primer before the stone chip?
Sorry if this seems unnecessarily long but I want to do it right and don't want it flaking-off a year down the line....... 
Your help will be very much appreciated! 
Paul.
