How to make the shambling dead shamble.

[ShadowLogan]

Several ideas come to mind that might explain how a Necromancer could do what you are seeking with skeletons, mostly speculation:
1. They use Zombies/Mummies primarily, with the animated skeletons (via spell/ability) to "surge" as needed instead of regulars
2. Unlisted ability/spell/ritual to create permanent Animated Skeleton in the same vein as the Zombie/Mummie/Golem
3. They gained access to a Animate (& Control) Dead Power Circle from Circle Magic (found in PF2E), either as a cross discipline magic OR it's unlisted as part of their normal access. That would give them access to 150 per level and duration lasts until the canceled.
4. A magical artifact with the ability, only more powerful. Example would be the Stone of Mal (pg166 RCB1r) that the Maxpray create as a Religious Artifact. Another example: the Sword of Bone found in LotD2 (pg176)
5. Techno-Wizard Item(s) they have acquired by some means (stole, commission, found) for them (RUE does allow Necromancers to work with TW, and IIRC there are Necro-magic TW items)
6. Rune Item (there is the Necron Staff in WB2/BoM, possibly other examples could be made/found)
7. The skeletons are misidentified D-Bee or "Monsters" (example Bone Fiend from LotD2 pg123-4, you can also be cursed in LotD to appear as a skeleton even a Dragon) that are in their employ and the statement is as if a report from someone looking on (and not an all knowing narrator).

[Grazzik]

Dead caravans should stick to roads or paths that follow ley lines so the necromancer can use absorbed PPE for mundane uses, such as keeping the horde marching. When travelling in a LL poor region, simply have your boney friends carry you as you meditate. Just make sure you give them good directions before slipping into a trance. However, I'd say most necromancers who go "off road" this way are lvl 6 or higher so their entourage lasts long enough for them to keep them moving between meditative top ups. Otherwise, as you suggest, they would need to stop frequently and the necromancer would have to dip into their personal PPE reserve.

Re missions that are out of LOS, best to use the Dead for simple tasks. The power description uses the examples of "destroy" or "kill". I like to use "pick fruit" or "collect eggs", things that don't move as they won't make chase if the target flees. They have to return before the duration expires, so keep the order short and to the point.

For an undead valet, Create Zombie (BoM pg 144) is a much better option as they have an IQ of 7! They can figure things out and could probably make you a fruit salad with the collected fruit or cook basic dishes like a frittata from written recipes (assuming written in very simple, direct language) using a microwave or electric stove (no cooking over flames!). The quality of their cooking may be questionable...

[Library Ogre]

1. They use Zombies/Mummies primarily, with the animated skeletons (via spell/ability) to "surge" as needed instead of regulars

Your zombies drag wheelbarrows full of skeletons (held together with leather straps), which you can animate as needed.

Or maybe you put them in environmental body armor and invite the Vashta Nerada.