Good to see you are keeping on it!
I hope you are not blasting with silica (general purpose/play) sand. If so you need to stop immediately and read this ->
http://www.silicosis-injury-attorney...ing_risks.html
If it's not silica then good for you and I hope others will benifit from this post anyway...
I use 60/80 garnet from
Lagrand Industrial either in a ventalated cabinet or with a resperator for large jobs.
Also, I have a sheetmetal brake you are wlecome to use for making your patches.
and here's a good read on rocker replacement