hatching Autocad

I hatch by pick points almost exclusively. Before hatching, I turn off layers such as Grid, Dimensions, and Notes -- layers whose objects I don't want defining hatch boundaries. I even have a special layer for that purpose, called Detail, for objects that aren't distinguished in one of those other ways but are nevertheless in the middle of what I know will become a hatch area.

Actually, with Detail and those other layers off, I almost never use more than one pick point per hatch entity.

But looking again at the original post, which did say that the hatched areas are already enclosed in polylines, and the problem is just that there are so many of them -- I think what archistud needs is a custom command that filters a selection set for polylines and then executes a hatch-by-Select-boundary-entities on each one. That would take me all day to write, but Roy probably sees the required code in his mind as he's reading my post.

Structure Browser panel is also very helpful to hide/unhide entities
Slow boundary detection can occur when very large xrefs or blocks are involved: if not required, hide them.

Enabling BoundaryDetection while hovering entities (set SelectionModes=4) combined with using the Quad cursor-menu, allows very fast creation of hatches.
Just hover the desired closed area: while the area boundary is highlighted, select the Add Hatch tool from the Draw tab of the Quad.
A hatch is created using the pattern with the name stored in the HPNAME setting: normally this variable holds the name of the most recently used Hatch Pattern.

After creating this first hatch, the Add Hatch command is memorized by the Quad as the most recently used command applied to a hovered boundary, so from now on, it suffices to hover a closed area and right-click to trigger this most recently used Quad command: Add Hatch.
In practice it means you can create like one hatch per second by simply moving the mouse over the next area and right-clicking it when it highlights.