If the gap is large enough that caulk alone may not fill it, Russell sometimes will use wood putty, an automotive filler called Bondo, or expanding foam sealant to fill the gap before caulking.
You are exactly right, I use latex caulk to fill the gaps and then paint when dry. This will create a seamless appearance. I've seen homes where the owners have caulked all their trim and it looks fantastic -- very clean.
Two-part epoxy is one of the top choices for patching large holes. Moldings, sills, doorjambs, baseboard or wood trim with damage or large holes can be repaired with epoxy. The two parts are mixed like dough and can be shaped before or after it dries. Polyester filler is used to repair holes in car bodies.
To fill large gaps in wood, use a two-part epoxy or wood filler designed for structural repairs. These materials can be molded and sanded to match the wood surface. For aesthetic purposes, consider mixing sawdust from the same wood type with glue to create a filler that blends seamlessly.
All nail, brad, and screw holes in trim are filled with wood filler. There are two main types of wood fillers: water-based fillers and solvent-based fillers. Water-based wood fillers are adequate for most interior applications.
You shouldn't use wood filler on wood that is already finished or on wood that is to be used in an exterior setting. Wood filler shrinks and hardens and will fail in the event of expansion and contraction, which is much more likely in exterior uses than interior uses.
When to use which? The easiest way is to remember is this: 🪵 wood to wood & gouges/scratches = wood filler. 🦷 seams & gaps = caulk.
If you're working with wood – be it filling gouges in a hardwood floor or addressing imperfections in wooden furniture – wood filler is your best bet. For drywall repairs, spackle is the clear choice.
For interior door, window and trim projects, acrylic latex caulk is usually a good bet. Use it for multiple projects, from installing wood paneling without nails to quickly filling in small drywall holes and cracks. Experts advise acrylic latex caulk is the best choice for baseboards.
The primary difference between caulk and spackle lies in their composition and intended use. Caulk is a flexible, waterproof material primarily used for sealing gaps and joints, and spackle is a putty-like substance designed for filling holes and cracks in drywall, wood, brick, and stone.
Holes in wood trim are best filled with wood filler. Nail holes in exterior surfaces, just as with cracks or gaps, can be dealt with using a good caulking. Take the time before you apply any paint on your next project to fill all of the gaps, cracks, and nail holes.
Choose latex caulk for gaps in non-humid areas of the house.
If you're fixing a gap between a floor and a painted wall that isn't exposed to a lot of humidity, such as a bedroom or living room wall, use a latex caulk. Latex dries quickly and expands slightly to fill cracks.
You can fill gaps up to 1/8". For wider gaps, it may be more aesthetically pleasing to insert a matching wood "sliver" or "dutchman" before applying the filler. This approach provides a more seamless and natural appearance.
Minwax® Wood Putty®
A non-hardening, pre-mixed putty color-matched to Minwax® Wood Finish™ stains and intended to repair minor scratches, gouges and nail holes. Various colors available.
I use caulking to fill those small gaps and cracks that form between trims pieces, and, between the trim and the wall. Position the nozzle near one side of the crack, pull the trigger until the caulking starts to flow out and slowly drag the nozzle along the length of the crack until it's completely covered.
Joint compound is a popular choice for larger gaps. This filler is used to bridge gaps between plasterboard seams, but it can also fill in holes and gaps in plasterboard. Joint compound is easy to apply, dries quickly, and is inexpensive.
For the long runs I use a paintable caulk. Run a thin bead of caulk to fill the gap and then run a wet finger or wet rag along it to smooth it out. You shouldn't need to sand. Caulk tends to shrink after it dries so it may require a touch up before you paint.
Two-Part Epoxy Resin Products
For small holes, a putty knife or epoxy ball suffices. For larger holes, consider mixing in sawdust or wood shavings to form a paste. Once the epoxy dries, sand it flush with the wood's surface. Then, paint or varnish as needed.