One thing you learn pretty quickly with 3D printing is that it's a rare event that you can take a completed piece of the printer plate and it needs nothing else doing to it.

If the pieces are printed with any sort of support for over hanging components, or printer bed adhesion then these need to be removed.
When the support is removed the contact spots with the actual workpiece always leaves little tags or bumps etc that need to be removed

There are lots of "burrs" that need to be removed.
As the printer jumps from one area of a workpiece to the other it often leaves fine airline wisps of filament in its wake and these have to be picked or cut off.
Ripples and ridges and Parts that don't fit neatly may need to be sanded.
More work may be needed for pieces to fit accurately together so "Some Adjustments" often need to be made.

Recently I started to print the components for a fractal vice and given there are around 40 individual pieces to be printed, many with sliding curved notched grooves the pot processing is pretty arduous. I've resigned myself to the fact that there is no way out of this and am using it as an opportunity to make this aspect as efficient as possible.

Here is a range of useful tools for this purpose.

Starting from the right
- Small cordless drill with range of fine bits
- Various cutters and blades
- Range of DMALL pliers - haemostats with fine tips are handy as well
- A dremel with a small chuck that can take various cutting/sanding attachments is very handy
- A metalworking scribe is very handy especially the right angled end.
- Range of small flat bladed screwdrives
- Deburring tool
- Range of medium - fine grit abrasive papers

One of the most useful Dremel attachments is this small (15mm diam) fine (0.15mm thick) micro circular saw blade.
It is particularly useful to cut supports into sections before busting them out of awkward places, especial so they don't put stress on sections you don't want to damage during the removal process.
I also found mounting it on a small buffing wheel spindle with the buffing wheel in place very useful as this limits the cutting depth

Beware! at speeds this thing is as sharp and fast as a scalpel but the buffing wheel setup I used partially save one of my finger tips when it made contact with the blade as it limited the depth of the cut. I didn't feel much when it happened and was even able to pull the blade out before any blood got onto the buffing wheel. It eventually bled like a stuck pig and later hurt like hell.

Of course if I had the fractal vice I would not need to hold the piece with my hands in the first place