How does one translate the Future Progressive? Does the tense marker 'pral' express both 'will be + present participle' and be going to' in English? Examples, "I am going to be studying." and "He will be studying at the library tonight."

Sometimes, there's not much difference between the simple future and the future progressive
You could use ap, a pral, pral, va, or ava alone or you may add the progressive indicator "ap" depending on the situation.

1.  "I am going to be studying."
     "Mwen pral ap etidye."

2.  "He will be studying at the library tonight."
     "Li pral ap etidye nan bibliyotèk la aswè a."
     
3.  Come pick me up.  I will be waiting for you inside the shop.
     Vin chache mwen.  Mwen va ap tann ou anndan magazen an.

4. I won't be able to drive home.  I'll be drinking beer all night. 
    Mwen p'ap ka kondi al lakay mwen.   M'pral bwè byè tout sware a.

5. Be careful.  They will be watching your every move.
    Fè atansyon.  Y'a pral suiv chak pa ou fè.

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