Emplastecemos con la masilla para madera.

It is the 1st-person plural present indicative of emplastecer.

So grammatically it means we fill / we apply filler / we putty over, depending on context. In instructions or demonstrations, Spanish often uses the present tense to describe each step of the process.

Not strictly. Emplastecemos is an indicative form, not an imperative.

If you wanted a real let's ... form, it would be emplastezcamos. But in practical instructions, Spanish often uses the present indicative to walk the reader through what is being done step by step, so emplastecemos... can feel like we now fill... in English.

Because this is the nosotros form of the present indicative.

With verbs like emplastecer, the spelling change appears in forms such as:

• yo emplastezco
• emplastezca
• emplastezcamos

But the present indicative nosotros form is simply emplastecemos.

So:

• emplastecemos = present indicative, we
• emplastezcamos = present subjunctive / let's

It is understandable, but it sounds a bit technical or specialised, especially in a DIY or repair context.

In Spain, depending on the exact situation, people might also say things like:

• aplicar masilla
• rellenar con masilla
• dar masilla
• enmasillar

So the sentence is not wrong, but the verb is not the most everyday choice for all speakers.

Yes, a little.

Out of context, many learners would expect an object: what are we filling? A crack? A hole? A surface?

In a tutorial, that object is often understood from the previous sentence or from the situation. A fuller version might be:

• Emplastecemos las grietas con la masilla para madera.
• Emplastecemos los agujeros con la masilla para madera.

So the original sentence works best when the thing being filled is already obvious.

Con shows the material or means used to do the action.

So con la masilla para madera means using wood filler / with wood putty.

It is similar to how Spanish says:

• Cortamos con un cuchillo.
• Pintamos con brocha.

Here, the idea is that the filling is being done with that product.

Because para here means for in the sense of intended for / suitable for.

So:

• masilla para madera = filler/putty for wood
• masilla de madera would sound more like putty made of wood, which is not the intended meaning

This is very common in Spanish product names:

• pintura para metal
• crema para manos
• pegamento para papel

Because after para, Spanish often uses a bare noun when talking about purpose, type, or intended use.

So masilla para madera works like a label: wood filler.

If you said para la madera, it would more likely mean for the wood in a specific context, referring to some particular wood already being discussed.

Both are possible, but they are slightly different in feel.

• con la masilla para madera suggests the wood filler being used in this situation, or the one already known from context
• con masilla para madera sounds more general, like with wood filler as a material type

Spanish uses the definite article more often than English does, so la masilla sounds perfectly natural.

Because Spanish normally omits subject pronouns when the verb ending already makes the subject clear.

The ending -emos already tells you the subject is we.

So:

• Emplastecemos con la masilla para madera.
• Nosotros emplastecemos con la masilla para madera.

Both are possible, but the version without nosotros is more normal unless you want emphasis or contrast.

In most of Spain, the c before e is pronounced like the th in think.

So emplastecemos is approximately:

em-plas-te-THE-mos

with the stress on ce:

em-plas-te-CE-mos

In much of Latin America, that c would sound like s instead.