The rubber plugs are OEM but, not every bike got them. CT70s NEVER came fitted with the grab handle; you are correct, in that this is Dax-only part and intended to help rock the bike onto a centerstand.
Etching & conversion primers can be had in rattle cans. Silver POR-15 works well, on the internal sides of the rim halves; the color is almost dead-on too. Just don't get any on the outside surfaces, UV turns it orange. There are also a number of good Hammerite knockoffs, outdoor paint that's very tough and seals the metal. Once rims have been blasted & painted, they really aren't difficult to redo...that's why I don't bother with any special prep, for my own bikes. When it's time to replace a tire, it's usually an ideal time to repaint the rim; they're usually blemished. The whole process (tire removal, prep & paint, reassembly) can be done in about an hour, under ideal conditions, if you're in a hurry. Overnight drying is more than enough for wheel paint, if you have patience.