Esperamos en el garaje hasta que la pared se secó y entonces guardamos la brocha.

Because esperamos can be either:

• present: we hope / we wait
• preterite: we waited

In this sentence, the rest of the context is clearly about completed past actions:

• la pared se secó = the wall dried
• guardamos la brocha = we put away the brush

So esperamos is understood as the preterite: we waited.

A useful thing to remember is that for many -ar verbs, the nosotros form is identical in the present and the preterite:

• esperamos = we hope / we wait
• esperamos = we hoped / we waited

Context tells you which one it is.

Because the sentence refers to a completed past event. The wall really did dry, so Spanish uses the indicative:

• Esperamos... hasta que la pared se secó = We waited... until the wall dried

Spanish usually uses:

• indicative after hasta que when the action is seen as real or completed
• subjunctive when the action is still in the future or only anticipated

Compare:

• Esperamos hasta que la pared se secó.
  We waited until the wall dried.
  → completed past event

• Esperaremos hasta que la pared se seque.
  We will wait until the wall dries.
  → future event, so subjunctive

That contrast is very common and important.

Because secarse means to dry / to get dry, while secar usually means to dry something.

So:

• La pared se secó = The wall dried / got dry
• Secamos la pared = We dried the wall

The se here is part of the verb secarse, which is often used for a change of state happening to the subject itself.

English often uses an intransitive verb naturally:

• The wall dried

Spanish commonly expresses that with the pronominal form:

• La pared se secó

The accent mark shows that this is the third-person singular preterite form of secar:

• yo sequé
• tú secaste
• él/ella se secó
• nosotros nos secamos

The accent in secó marks the stress on the last syllable: se-CÓ.

This helps distinguish it from forms or words without that stress pattern, such as:

• seco = dry (adjective, masculine singular)
• seco can also be a present-tense form in other contexts

So the accent is both a pronunciation marker and a grammatical clue.

Because Spanish often leaves out subject pronouns when the verb ending already makes the subject clear.

In this sentence:

• esperamos already tells you we
• guardamos also already tells you we

So nosotros is unnecessary unless you want to add emphasis, contrast, or clarity.

For example:

• Esperamos en el garaje... = normal, natural Spanish
• Nosotros esperamos en el garaje... = more emphatic, like we waited

Omitting subject pronouns is one of the most natural features of Spanish.

Because en describes location: they were in the garage while waiting.

• Esperamos en el garaje = We waited in the garage

By contrast, a or al usually suggests movement to a place:

• Fuimos al garaje = We went to the garage

So here the sentence is about where they waited, not about going there.

Here guardar means to put away, to store, or to put back in its place.

So:

• guardamos la brocha = we put away the paintbrush

Guardar can sometimes be translated as to save, but not in the computer-money sense most English speakers first think of. Its core idea is more like:

• keep
• store
• put away
• keep safe

Examples:

• Guardé las llaves. = I put away / kept the keys.
• Guarda el móvil en la mochila. = Put the phone in the backpack.

So in this sentence, after the wall dried, they put the brush away.

Because brocha usually means a paintbrush, especially a broader one used for painting surfaces like walls.

A pincel is usually a smaller brush, often for:

• finer painting
• art
• detail work

So with la pared in the sentence, brocha makes very good sense. It sounds like the kind of brush you would use to paint a wall.

In Spain, that distinction is very natural:

• brocha = wall/house-painting brush
• pincel = finer brush, artist’s brush, detail brush

Yes, the sentence could work without entonces, but entonces helps mark the sequence of events more clearly.

• ...y entonces guardamos la brocha = ...and then we put away the brush

It adds a sense of next, then, or at that point.

Without it:

• Esperamos en el garaje hasta que la pared se secó y guardamos la brocha.

This is still grammatical, but entonces makes the timeline feel more explicit and natural in narration:

1. we waited
2. the wall dried
3. then we put away the brush

So entonces is not required, but it is useful for connecting events clearly.