Patching and Plastering - Redoing a skim

Hi,
I've just skimmed a wall with finish plaster and i left it a little too long before the polish so i'm not happy with the result. I'd like to go over it again, so my question is can I just put another skim straight on top of smooth new finish plaster?

I'm assuming I can't seal with PVA first, since the work i;ve just done would need to dry out for a week or so?

Thanks in advance for any help

How bad is it? Maybe you can go over it with joint compound and flatten it out.
If you want the polish of real plaster you should do it like this:
Let it dry a couple days
Paint it with a good bonding agent like Plaster Weld by Larsen's Products.
Let that dry. It will only take an hour or so
Mix up some Veneer plaster base coat like Imperial Base
Let that set.
Finish the wall again.
How large is the wall?
Can you finish it in one gauge?
Do you know how to make a joining?
What finish are you using?
Is this thin coat plaster or real three coat work?

How bad is it? Maybe you can go over it with joint compound and flatten it out.
If you want the polish of real plaster you should do it like this:
Let it dry a couple days
Paint it with a good bonding agent like Plaster Weld by Larsen's Products.
Let that dry. It will only take an hour or so
Mix up some Veneer plaster base coat like Imperial Base
Let that set.
Finish the wall again.
How large is the wall?
Can you finish it in one gauge?
Do you know how to make a joining?
What finish are you using?
Is this thin coat plaster or real three coat work?
It's the front face of a chimney breast, 2.5m x 1.6. I've done a layer of bonding, then hardwall with guides to bring it straight and plumb, then I sealed that with PVA 1:5 then 1:3, then the skim of multifinish, all Thistle plasters.

Once rubbed down and painted it would do okay, not professional work but I don't think you'd spot it without looking for problems. It's more that i'd like to both practice my finish plastering and do a pro job, so i think i'll take your above advice.
I assume i'll need to place new corner beads on the outside corners?

A bit more work than i was hoping for to redo it, but there's no particular rush for the job unless you count a girlfriend who is prone to nag and suggest getting the builders in, but I find turning up the ipod solves that one.

If it's good enough that I wouldn't spot it without looking for problems it must be good. If you want to practice find another project.

I don't know what Thistle plasters are. Are you in UK?