Hi and welcome!! I‘m not qualified to give a lot advice, I struggle a bit myself I‘m afraid and have had to resort to DIY‘ing it, purely because I can‘t find a groomer locally. (I live in the sticks, in Germany!).
Just a couple of things I would say though - I was badgered into leaving Humphrey alone at the groomer the first time and although he was ok, in retrospect I wouldn‘t do it again. I think its reassuring for you and the dog to at least be able to see how she/he works and handles your dog and a good, sensitive groomer should understand and accept you being there, - you are the customer after all! ( I returned to find she‘d expressed his anal glands and also shaved his whiskers )
I find handstripping tough on my hands which, at knocking on 70, are getting a bit arthritic, so I do use a coat king but only every couple of months or so. They‘ve now brought a „dull“ version onto the market which guarantees that it doesn‘t cut the hair at all and I use that now (I have a fine 20 tooth ). A fine spratts comb with an elastic band woven through will pull out a lot of the undercoat.
Humphrey has a very wavy coat so it tends to grow in all directions and I can‘t get that sleek look but we live in the country, so I need a practical trim.
I‘m sure there will be others along soon who have more advice, I just really wanted to point out the new version of the coat king as possibly others aren‘t aware of it.
Good luck!