Stripped most of old flakey paint off, drilled and tapped threads, next is to make some blanking plates and have it soda blasted,

 

I'd skip the blanking plates and go get a couple expandind test plugs or cut a couple wood plugs and tap them in place to protect the bores, bolts in the threaded openings. FWIW soda blasting is so mild I doubt will even remotly remove any of the paint that is still adheared to the metal.

If it were me, I'd get a jug of citrus paint stripper (unfortunately we are no longer allowed to have paint strippers with methayline chloride in them) paint it on shove it a trash bag and come back a copuple hours later or the next mornign and then pressure wash the part to remove all the bubbled up paint. Repeat as needed until clean.

 

You can also buy silicone plugs specifically made for stripping / painting in a variety of sizes and assortments. Very handy and most paint / powder doesn't stick to them. If you are sending it out to be blasted, I'd imagine any commercial place has all the covers/plugs they would ever need.

I've often used blue painters tape on the inside of larger openeings. It hangs in there surprisingly well if your not stupid with the angle of the blast stream.

If you are planning on painting / powdering the cover, blasting with glass frit will give a better surface texture for adhesion without eating too deep into it and make short work of the old paint. Unless you are really trying to preserve the OEM aluminum texture, but a repaint will cover that anyway.

Soda blasting is really only useful for when you absolutely need to not have any leftovers in cracks and crevices, since it's water soluble it can be dissolved out with washing.

 

 

I work in metal fabrication and we do MUCH powder coating and wet spray all day and every day......you want proper sized silicone plugs for the threads, and that surface is no where near being ready for paint or powder coat. You also must de grease the surface as well after properly blasted, might even gas out everything and cool down before powder or paint.

 

Another tip would also be get all the part that are going to be powder coated or painted ready to go in one batch. It'll be cheapers and there will be no color deiviations. IT would also be better to get them all prepped at the same time. Onesie twosi gets expensive.

 

Thank you any tips appreciated