I've had the same problem with some of the plants at my job. I was able to rectify the problem with Limidacloprid sold by Bonide as Systemic House Plant insect control. There is another systemic insecticide sold by Bonide Disystol or Disulfaton don't buy this especially if you have kids/pets it's a neurotoxin.
You may find Limidacloprid sold as Marathon. Apply it to the top layer of soil mIx it in then water thoroughly.

It's hard sometimes to properly identify a bug that is barely visible to the naked eye. Sometimes we can tell what kind of damage the bug is doing to have a better idea what it is we're fighting.
Generally though, all of them can be expected to be knocked off by simply hitting them with a stream of water.
It may be difficult to do this if the plant has to be moved and its of size that limits such a move but to be effective, that is often what HAS to be done.

One might also suggest that by spraying somehting unknown, we're really not doing the plant any good if the bug is not affected.
Now for thrips, one of my guides says to use "rotenone", "pyrethrum", or petroleum oils--the other half of dormant spraying.

The damage caused by thrips is distortion of growth of tissue. Rasping of leaf edges and the leaf itself might also identify it.
Injury can appear as silvered areas that are speckled with dark spots. Foliage might appear to be blotchy and drop off.
Flowers might be streaked or look distorted and they may fail to open.

Your description however, might apply to "whiteflies" which do have white bodies and wings. They flutter about in a white cloud when the plant is disturbed. The young of whiteflies attach themselves to the undersides of leaves.

And there's the rub...while yuo might see and/or attack the adult today, you may be having to treat the larvae tomorrow.
Most of these bugs have very short stages of development, usually within a week from egg, to larvae to adult.

You might wish to treat the soil as well. They can be expected to be within an inch or two of the surface.
disturbing the soil with a dinner fork might open them to be discovered or treated.

I'm not a fan of systemics unless there is a directive to use one for a particular pest. Some systemics are very harsh and I imagine can do more damage than what the pest does. I suppose if one has experience with one, the gardener can put his faith into its use but I think unless the label identifies its use on such pests, its better to look elsewhere.

I'm a fan also of using a hand-held vacuum for sucking up those sucking insects if I can see them--even if I cant see them, such vacuuming cant do much harm; maybe just remove some dust from leaves and crotches.

Before going to extremes of insecticides, why not use the old stand-by...soap and water.
32 parts water (quart) 1 part dishsoap or to make a lesser percentage 3/4 part or even a half part. That makes a 3%,
2 1/2% and 1 1/2 percent.
Spray on, wait ten minutes after coating all surfaces, top and bottom, then rinse with tepid water the same all surfaces. The soap will coat the bugs and since they breathe air will suffocate. The water rinse will ensure the soap doesn't stop air and water from being taken up by the leaves.

In any case, when one plant is so affected, it is a good idea to isolate one from the other to prevent cross infection.

Whatever method of fighting is carried out, the usual repeating of such measure has to be cosidered. As noted, the stages of development can be so rapid that if one only uses one treatment, it may not do in the young that are now the enemy.
If we consider a cycle of devlopment be 10 days, two weeks, then re-treatment every 7 days, for 20 days should break the cycle and then constant vigil for any sign of return.