you would use the correct amount of makeup for the look the client wanted and their skin complexion and the bridesmaids coverage tastes regardless whether they are the bride or bridesmaid.
never scrimp on a services when I comes to products for bridal makeup.
You need to ask what the client wants doing on their face, unless it has been agreed beforehand with bride that everyone is happy to have the same look.
Most brides will not want the same makeup look on their bridesmaids as on themselves. However they may want the bridesmaids to have all the same look or they will ask the for them to choose what look they want themselves makeup wise.
Gone have the days where brides want their bridesmaids looking the same, many now realise that by having their bridesmaids choose their makeup looks and coverage means a happier bridesmaid and that looking all same looks old fashioned and many bridesmaids now dont wear the same style or colour of dresses anymore on the big day.
People will book you for style and flare and if you do just one look so it's quicker for you, people will feel cheated as many want different looks to suit their own complexion and outfit etc. you being paid to accommodate the client not yourself.
For bridal you need to work with profection, but very quickly. Bridesmaids 25/30 mins each and bride 45/60 mins.
I can do roughly 10 people on my own with no assistance, but I have been doing it 16 years!
You may never get to do trials on everyone as this can be a too expensive for the bride or her bridesmaids to pay for, you have to be confident in you ability to work without trials and think quickly on your feet on the day what looks you can do for each person.
The bride and her bridal party should never be delayed or over worked on due to your over perfectionism, as this can come across also as you not have faith in your own work and your lack of confidence and this will rub off on the bride and her bridesmaids and this when they start to get anxious, uppertty and short tempered as they will get nervous that you can't do the job.
It sounds to me you need a bit more practice with looks and more confidence before going into weddings, as you will be looked to on the day for advice on looks and fast yet flawless service.