With Shetties I would expect them to be up an sucking in an hour max, normally within 20 mins.
Stomach tubing is easy enough if you go gently. Measure the tube on the outside of the lamb so you know what length to use to reach from mouth to belly, very gently slide it down the throat, any resistance and stop, withdraw and try again. If you get the wrong hole lambie will cough and splutter unless unconscious but you shouldn't be tubing an unconscious lamb anyhoo. I use a 50ml syringe with the plunger removed as a funnel to pour colostrum into as it fits a treat into the tube and has graduations on it so's you can see how much you are giving
Some people say to dip the end of the tube in milk before tubing, but I don't as I worry about it getting inhaled if I get the wrong hole.
Good luck, I reckon you will be fine with them now you have em penned