I think that this is the set I have, they are good but I've not tried any other brands, which may be just as good or better.
Having a range of sizes is good, but the very finest ones are the most useful.
I use them to pick out helmet vents, edge eye lenses and shadow places where armour plates overlap; I find them easier to control than washes and oh so much more exact than painting very fine black lines. If and when I get to free-painting markings I'll try outlining them in pen too.
In general it takes very little to give a good effect.
If you have any shields, you can make more by making moulds with this stuff and using Greenstuff or Milliput. It's really easy to use, and is reusable.
I was having similar problems last year and got one of these. Lots of different brands available, mines got three speeds and just makes the whole job a whole lot easier.
Deal: Rotary Tool Cordless, Ginour Rotary Tool 3.7V, Cordless Multitool with 32PCS Accessories, Speed 5000-15000rpm, USB Charging, Suitable for Small DLY Work Polishing, Engraving, Cleaning, Drilling
Do you have any original plastic ones? If so, get some of this stuff and use greenstuff/Milliput to cast your own. It's stupidly easy to use and can be reused over and over.