sandblasting? if so, can you rent those?
I don't think you want to sand blast inside and create an untenable amount of dust. If the original coat of paint on the surface is an oil base paint PEEL AWAY I will remove it all. If the first coat of paint was latex (water based) onto a porous surface it actually seeps right inside. PEEL AWAY 7 will do your job. In both instances you will remove the paint without creating all sorts of environmental problems