You do not need an expensive scale - not even for Pyrocat.
The only substance used at fractional grams is phenidone (well, potassium iodide also).

Mix you phenidone on very pure alcohol - I use 2% solution (2g in 100cc alcohol). It lasts a long time. If you have some hydroquinone, add a pinch of it to the alcohol before adding the phenidone (increases keeping properties).

10cc of this solution=0.2g

Jorge O