I inject using noromectin/ivermectin BUT ours are all traditional breed or kunekune and very laid back so milling around them with a syringe and needle doesn't present any issue - yours may be a little feistier? The slap shot gives you a longer tube to allow for movement away from you without losing the dose
Otherwise there's a fab thing called a masterject for injecting at distance.
If the thought of jabbing them brings you out in a cold sweat there are a couple of oral treatments - panacur (best IMHO) or flubenol (passable) but I don't think either of these will treat external parasites, so you'll need a pour on or powder for lice/ticks etc. and you'll have to separate them at feed time to make sure they all get the proper dose (or make OUTDOOR jam sandwiches and load it with the meds
)
HTH