It's not usually necessary- if the first coat of emulsion is patchy or insufficient, then just apply one or two coats more.
you should put 'an' before electric because the first letter of the next word is a vowel
No.
An or the
No.
you should do it about 15-30 seconds before you turn
Yes, you should put a comma before "as" when it is used as a conjunction in a sentence.
put your goggles on
before
Detergent should be put in before adding clothes when doing laundry.
Mortar should cure for at least 24 to 48 hours before it is safe to put weight on it.
You should put a comma before a person name if you're talking directly to them. ex- Please come here,Lily.
before.