Can't remember for sure but think the series IV later models have automatic parking brake shoe adjusters and not the toothed wheel, I couldn't understand why there was no removeable rubber bung on the drum to poke the screwdriver inside to adjust the shoes.
Basically calliper off, calliper carrier off,drum off after removing the 2 countersunk retaining screws, clean everything with brake cleaner, check everything that should move does or free off, if the brakes shoes still have minimum lining thickness clean them with some coarse grade sandpaper to remove any glazing.
Lubricate all moving parts including where the shoes contact the backplate and pivot points.
If the adjuster is manual refit the drum then turn the adjuster until the drum is locked then back off the adjuster until the drum is free to turn again ( very fiddly through the hole, not easy to see or work out which way to flick it with a screwdriver).
Obviously make sure the parking brake is fully released and the front wheels are chocked ( there's one in the spare wheel well)