Black Aphids on conservatory Yucca

I've got black aphids (at least think they are - they are very small) on my indoor (conservatory) Yucca.  I've taken the Yucca outside this morning (which wasn't easy because its over 6 foot tall and heavy) and given it a good blasting with the jet watering nozzle on my garden hose, and I think I've washed off most of the aphids and also the sticky black spots they have left behind.  I also had some leaves encrusted with Aphid shells (I assume they shed their skin).  I think I've hopefully got the majority off but not sure.  If they come back again, is there anything other than something like Provado to get them off.  I'm not really happy using outdoor chemicals at the best of time, and not really happy using it indoors so something safe and not too messy would be helpful.  I wondered if something like house fly spray would be sufficient, and although not spray directly on the plant, spray in the general direction and then leave the conservatory shut up for an hour or so?   Or is that just a lazy mans way of thinking!