Ive used ivermectin to worm them, and feed them DE once a month or so and have never seen any real worm problems with them. A few drops of iver on the neck can get rid of mites and lice too. It won't work for tapeworms though. While it may not be the 'recommended' wormer for them, it works extremely well, and since it's just me eating the eggs, I don't worry about 'pull days' since I don't sell them, and the people Id give them to, aka my few friends, are not afraid of Ivermectin even if they did get any in them, in fact like me, have tubes for other purposes as well.
No they typically don't like de worming, or lets be honest, ANY procedure that you have to hold them and 'force' anything on them. Even when you try to pretend it's cuddle time, for some odd reason, they seem to know better.
If a bird is sick, Ill take her upstairs and treat her in the bathroom because it's easier to work on the sink counter, otherwise general worming etc, I get crappy clothes and do it outside then leave the clothes outside and spray with bleach water / alcohol and let soak in disinfecting soap before washing them. yes this IS a lot of overkill but if im flushing out worms, I do NOT want to bring them to the INSIDE birds.
Aaron