Repairing Steading Roof and Sarking on Building

[Donstar]

Hello,
I've got a steading building and in some parts I needed to replace some slates, and replace missing ones. Also in some areas I'm needing to remove a couple rows of the bottom slates to replace the sarking.
My tiles are double nailed on the top edge which prevents me sliding tiles sideways to get access. How on earth do I manage to place in a new tile and nail it if I cannot move surrounding tiles? And how do I go about removing 3 or 4 rows from the bottom edge and then replace them securely?

[welsh brickie]

you use a slate ripper to remove the slates, its a long piece of steel that slides under the slate with a hook either side to grip the nail, then you bang the ripper down with a hammer to remove the nails ,and the slate will slide out.
To fix the slates back, a clip / metal strip, is nailed to the batten, then slide the slate over it and the clip is bent over to secure the slate.
For single slate repairs, you can use adhesive like silicone or gripfill to fix into position

[Donstar]

Does that mean if I remove the bottom 4 lines of slates to replace the sarking board I'll have to have the bottom row all held in place with metal clips?