Translate: "-ing" - gerundio form without estar?

Translate: "-ing" - gerundio form without estar?
 

Hello.

I'm trying to say "I spent a lot of time researching the technique"

"Pasé much tiempo ________ la técnica"

I know the verb to use is investigar - and the direct translation to fit the form would be investigando. However, I cannot remember ever using the gerundio form without estar in front. Any help on which form of the verb I should use?

Thanks!

There are quite a few ways of using the gerundio without estar:

Llevo mucho rato esperando.
Va cobrando importancia.
Vengo diciendo que es imposible.
Marta siguió cantando.
Vi a los niños jugando en el parque.
Salió corriendo.
Nos divertimos bailando.

:)

That's similar to what I'm doing - so long as this is correct, I would assume I'd be okay to simply use investigando?

Thanks :)

Yep. In all the cases cited, the gerundio is acting as an adverb.