I use pure isopropyl alcohol and microfiber with my lenses and it does the job nicely, besides dust it removes all fatty residues that I guess come from flux.
"I think you are facing staining and flux spatter issue (not dust). You need to use a clean solvent to properly clean the glass lens surfaces. Rubbing alcohol has other junk in it that just leaves a mess on glass surfaces and if your lenses are plastic will also damage them (fogging them).
As @arbaman stated you need to use isopropyl alcohol but not the cheap stuff! As it to has junk in it too! You need reagent quality (90% or better) or a good photography lens cleaning fluid. As you need something that will cut through the flux sprayed and the vapors deposited on the lenses. On the eye pieces you have the skin oils from your eye lids.
Make sure the micro cloth is rated for lens cleaning (some are too coarse) As you don’t want to scratch the lenses. Or, use proper lens cleaning tissue. You also don’t want to wet the lens but the cloth as it will often seep into the barrel making a mess on the other side of the lens which might not be accessible to clean. Q-Tips also work but the amount of cleaning fluid needs to be monitored as again you don’t want a very wet wipe (just damp!) And you’ll likely need to use a few changing them often if the surface is very dirty. Wash the micro-cloths out throughly using a detergent that has no softer or scent fresher as you don’t want anything left on the cloths. Frankly, I just cut them up into small 3 inch pieces and toss them once they are dirty.
Use the can’ed air carefully! Short blasts and before I use any cleaning fluid as it can push it in making a bigger mess. You don’t want the liquid to exit so don’t tilt or shake the can while using."
"Go to Edmund Optics and purchase stock number #52-105. Use forceps, and fold the paper so you always have a clean side up. Apply a little 92%+ Isopropyll (should be easy to get 99%) and you can get any reflective surface streak free with almost no issues.
