I assume this is PAINTED moulding? Using a nail punch can be tricky. You have to find the right sized nail punch to properly sink the nail. If the punch is oversized, it tends to slide off the nail. If it's undersized, there's usually not enough force to punch the nail in properly.

Any gaps that are more than a 1/4" wide will not hold caulking very well. So, as long as the gaps aren't big, you can fill them with a flexible caulking. I use MaxFlex from SW but there are similar versions such as Big Stretch, etc. Keep a damp cloth handy to smooth out the caulk and remove any excess. Let it dry and harden up for 24 hours before painting.

Nail holes can be filled with spackling. It shrinks, so you will have to fill it more than once. Sand off any excess, prime the area, and paint.

Gaps around the ceiling USUALLY disappear once spring comes and brings in more humidity allowing the wood to swell and return to position. In winter, it's so dry the wood shrinks ever so slightly causing rafters, joists, framing to move enough to create a gap. Filling those type of gaps usually doesn't work because when the wood swells and moves back it pushes the caulking out of the gap making an ugly glob of dried latex caulking.

 

Painters Putty will not shrink like spackle does.

 

can you suggest which brand of painteres putty
one i bought from Home depot, goes bad after few weeks
gets yellowish

 

There are plunger type nail sets that really help end the slipping off the head problem--
look at your neighborhood store in the nail set display.

 

Nail Punches as noted above.

For painted stuff...I've been using Alex caulk. I use it in the joints....drys quick...paintable....shrinks a little...so it takes two coats...not a biggie....I go around...fill holes...sand...prime...touch up any holes that need a 'little more'.....paint...done.

 

The downside to painter's putty is indeed the "yellowing" effect. You will have to prime the puttied spots with an oil-based stain blocking primer or the oil in the putty will wick into the finish.

 

You can buy syringes from Lee Valley with blunt nose needle tips. When filling finishing nail head holes I would use those blunt nose needles to fill those holes with latex caulk.

First, use a Q-tip to coat the inside of the syringe barrel with Vaseline (or any oil based grease).
Then, dispense some latex caulk into the barrel of the syringe.
The insert the syringe plunger, but press it to the side of the barrel to allow the trapped air inside the syringe barrel to escape.
Then, fill in the finishing nail head holes with latex caulk dispensed from the syringe.

And, when you're finished, just remove the blunt nose needle tip and squirt the remaining caulk into the garbage and wash everything off with water.

Those syringes also work well for filling joints in painted moldings like baseboards and shoe moldings.

 

For best results, hit the nail holes with the putty and them hit them again with the MH ready patch. Then sand a little bit and it'll be completely invisible. But that is for a high end spray job. I usually just squish some extra paint in there with my brush.

 

Dap painter’s putty will yellow. I stopped using it years ago. Crawford’s painter’s putty doesn’t offer that problem or at least it didn’t for me. When storing it for long periods of time make sure the putty is completely covered with water.