I just suffered a wheel/curb incident a couple weeks ago. I went and talked to a wheel repair shop, that is the extent of my 'knowledge' on the subject.
IN my case, I ended up with a spot about 11" long, where the 'ridge' at the edge of the wheel was ground off due to the impact. The area where the bead of the tire was not affected, and the rim appears to still be good, aside from the cosmetic damage.
The approach the shop would have taken, when I showed him the photo, was likely going to be to weld some material back on along that edge, and re-shape to the proper profile. He did state that there could be challenges due to the machined finish, that you may not be able to completely get the new 'seam' to disappear, and have it stay clean, leading to possible cracking and pitting along the patch. While he did not say it could NOT be done, he did suggest that a new rim might be the better option, at least in my case.
So that is the route I'm taking my repair, filing an insurance claim, since the cost of the rim (ridiculously expensive), a new wheel bearing assembly, and a 4-wheel alignment was nearing $1600.
The cost for the repair was likely to be in the $300 range he told me. Online research has shown me that was pretty much in the neighborhood for a couple other wheel repair services I checked on.
I'm not sure which of the 20's you have, we have the split 5-spoke, some call it 'flower' pattern (I hate that term, LOL). While you can find rims on E-bay for under $500 each, the list price thru my dealer was $852, for the bare rim.
Just sharing what I've learned on the subject, I don't really have much I can share as advice.