Using the SWG might work, but there is a reasonable chance that the chlorine demand from the pond water will overwhelm it. You want to make sure the water gets up to shock level after adding the pond water and the best way to do that is to have some bleach, or other chlorine source, on hand to add after you add the pond water. Depending on how "dirty" the pond water is it could use up all the chlorine and the SWG would not be able to keep up from there.
I would build up the chlorine level in advance with the SWG, add the pond water, then test the FC level and add extra chlorine to bring it up to shock level. The SWG should then be able to keep up from there. You want a good shock to clear up anything that might be in the pond water. Shocking requires bringing up the FC level quickly. A SWG can't usually do that quickly enough, even with some advance buildup, thus the need for some extra chlorine.