Definitely make sure whoever you get to blast them uses something that will not dent the metal.
If you can find someone who uses crushed walnut shells or baking soda it would be ideal (I am pretty sure those will be safe on the metal)
The silicone is super easy to replace...I will do a write up when I redo my BBSs. In the mean time you just want to make sure you scuff up the powder coat/paint where the lip and barrel meet - where the silicone is going to go. I used 400 grit sand paper then some scotch bright. You want to make sure you clean the said surface really well. I use a paper towel and some general cleaner (kitchen lysol or 409 or whatever) until the paper towel stays white when you wipe it. I used Aluminum/Metal Silicone from Lowes made by GE. It is a black and blue tube with Aluminum and Metal Silicone written on it, haha....oh look I am nice and searched on Google for you:
That says Window and Door but the bottle looks the same.
They're like 6 bucks and you can pick up a 1 dollar caulk gun in the same isle. You have to shove a screw driver down the tip when you open it otherwise the it to poke a hole in the seal that you can't see. If you squeeze on it long enough without doing that it'll explode/break out the back....ask me how I know.
Anyway, just lay a small bead of that down in the groove and smooth it out with your finger, let it cure for 24 hours and push on it to make sure the edges of it don't come up and you're good to go.
It takes about 10 mins a wheel max to do the whole process.
PS - I would do powder coat, its stronger and you don't have to do anything.