If you manage to arrange the sample properly, I'd suggest scanning electron microscopy (SEM) techniques. For very accurate measurements, if the sample allows so, you can try atomic force microscopy (AFM).

If u need to find out thickness about your prepared any materials, deposited films or membranes Using thickness meter . otherwise before coating and after coating to weighing electronic balance.

for electrochemically deposited coating material - you can count the charge during deposition process and calculate it

I recommend crosssectional FESEM to check the thickness of the coating  > 25 nm.  If it is less than 20 nm, use HRTEM.

I suggest FESEM for thickness measurement.

I think FESEM is good for this purpose

You can use FESEM. We also used this technique.

if the coating is isolating you can use microwaves like the FSC 1/7.

See the publication in german, there is also an English version at FITM.de

http://fitm.de/wp-content/uploads/2015/10/Paint-thickness-measurement-on-CFRP.pdf

Article Mikrowellenbasierte Dickenmessung von Lack auf CFK