so i have the filler work done and only have the glaze on the hood left to do

that leaves my next step in this paint job, high fill primer and block sanding

my question is about block sanding the primer

i have a couple blocks like this one
but i am not sure it that is the best type for block sanding
should i keep using the stiff board with the thin foam on the bottom or should i get some dura-blocks like these

i have never used a dura-block, are they fairly solf and flexable?

thanks guys
Jon