First Contact is expensive, but for small optics those bottles will last you many cleanings. It's a shame they don't seem to sell the little brush bottle on its own.
For simple viewing optics, just about anything mildly adhesive would probably be fine for removing particulate, and you can always follow up with a suitable solvent to remove residue if necessary. Minute levels of residue aren't going to be a problem for a microscope like they could be for laser optics.
On the other hand, how much of the particulate on your microscope is likely to be hard enough to scratch the lens/coating? Perhaps if you've been excavating PCBs under your microscope and throwing up all kinds of glass particulate that would be a concern, or perhaps if you live at a beach with really fine sand, but for normal household/office dust it's mostly skin cells, right? In which case I would probably just use a non-abrasive wipe and some IPA and be done with it. Of course the best thing to do is keep the microscope optics clean in the first place, by keeping it covered when not in use and perhaps fitting a protector over the objective (cheap barlow lens or filter) if possible.