Insulating the motor for DCC decoder install

[trainstrainstrains]

I understand it is always advised to isolate/insulate  the motor from all else when installing a DCC decoder. Has anyone advice on the best way to do this? How exactly it is done? With What materials?
I imagine there are a few variations on how to do this depending on the type of motor, how and where it is mounted and whether it is DCC ready or not.
Here is a list of the n scale  locomotives I plan to convert:
At least 3 of these have the  motor and pickup on the tender so if there is no space anywhere I will mount decoder and speaker in car behind.
Bachmann American 4-4-0.
Atlas Mogul 2-6-0
Arnold  2546 KBAY P42  4-4-0
Fleischmann piccolo 7159  4-6-0
Kato 2007-2  C57  4-6-2
Bachmann Spectrum B&O EM-1  w/DCC - Baltimore & Ohio #7614 2-8-8-4
About the non Bachmann locomotives I have seaked advice in the nscsle.net forum.
Thanks in advance.

[Ken G Price]

If the motor touches any part of the frame, that is where it needs to be isolated. I, and many others us Kapton tape, 1cm wide for this.
Some decoders come with tape. At least the Digitrax ones do.

I run diesel/electric engines and most I have are DCC ready. 3 older split frame ones I had to isolate the motors, and the solder the wires from the decoder to the motor contacts.

It is not really too hard, but just takes observation and patience. No rushing is needed.
Oh, and proper soldering.