What can I use as a non-fouling exterior filler for countersunk screws in vertical painted wood?

Question

I mostly work with exterior torx drive screws if I'm not nailing up.

What technique/material is there for filling a the hole of countersink without fouling the drive on the screw head, yet allows sanding flush?

My current technique is to finish the complete assembly, then remove screws one at a time, paint the hole completely, let paint tack up, then redrive the screw, and go on to the next one.

It's not bad, seals the wood, but the screw color never comes close to matching the paint, and is rather time consuming. So filling 1/2 way with a non-hardening, non-dying, etc material (talking years here), followed by a traditional putty would be one approach, but exactly what materials?

Wood plugs are out as not generalizeable to obliquely driven screws. Instead, looking for the analog of backer rod for caulking deep joints, e.g. cement.

Answer 1

One solution is to use a syringe to apply a dab of grease onto the drive head, for example, the torx divot, then use your putty of choice to putty over every thing and fill flush.

Answer 2

• Assemble your structure, including drilling, countersinking and driving your screws.
• Disassemble your structure.
• Paint all the individual pieces.
• Reassemble the structure, placing screws into prepainted holes.

If it's that necessary to get the screw heads to disappear, then your best bet is to cover them and paint over them.

Alternatively, take the screw to the paint counter and have them color match your paint to the screws.