I would always want to strip, prepare and degrease a RTR chassis before any paint job of this sort. Both so that the new coat of paint adheres well, and to ensure there is no paint where it is not wanted on pick up wipers, and in small joints in the valve gear.
If it is a consolation, there is an additional benefit in doing this strip down on the Hornby 8F, and many other Hornby locos of similar vintage. The electrical connections from the loco wheel pick up wipers are made by rather poor flat face-to-face contacts, and the whole chassis block is live. It is very little additonal trouble once the chassis is stripped to substitute soldered wire connections; and this wil pay off in long term running reliability, particularly if it is intended to fit the loco with a DCC decoder.
If it is a consolation, there is an additional benefit in doing this strip down on the Hornby 8F, and many other Hornby locos of similar vintage. The electrical connections from the loco wheel pick up wipers are made by rather poor flat face-to-face contacts, and the whole chassis block is live. It is very little additonal trouble once the chassis is stripped to substitute soldered wire connections; and this wil pay off in long term running reliability, particularly if it is intended to fit the loco with a DCC decoder.
