Re:
What were the surfaces of the cups and/or cones like, nice and smooth, or pitted?
Also, with cup and cone style bearings, whether its wheel bearings, headset or bottom bracket bearings, you need to adjust them so that they are "just so", not too tight, which will make them not spin freely, and not too loose, so that you get play or slop in the bearing. This can be a bit of a faff and is much harder if you don't have the correct tools that allow you to hold cone part of the bearing and tighten the lock nut to it.
More info:
https://www.parktool.com/blog/repair-he ... adjustment
Cup and cone hubs generally use two different sized ball bearings, with smaller ball bearings in the front hub. These are typically 20 x 3/16" for front hubs and 18 x 1/4" for rear hubs, but there are some hubs that take different sizes. You can buy loose ball bearings at some bike shops and on Ebay:
https://www.ebay.co.uk/itm/Weldtite-Bik ... MXBs-WpoXw
I don't recognise the hubs, probably fairly generic and given that they have solid axles, probably not particularly high quality. Good quality cup and cone hubs from Campagnolo, SunTour and Shimano, etc. can last for ages and run really smoothly, but some of the cheaper ones just aren't as well made and will never run as smoothly, no matter how well you adjust them.