You are doing the right things - moving slowly, sitting next to their cage talking to them, offering food from your hand.
They will gain trust in time but a lot of patience is needed and for some piggies, two months just isnt long enough.
Ensure you dont stand over them - this can be scary for them. Also make sure you announce yourself as you enter - predators are silent so if you are also silent, then that scares them.
What happens after a little while if you hold some food in your hand and offer it to them? Do they hide the entire time you are in the room or do they come out eventually and take food from you if you sit with them gently talking to them?
Understanding Prey Animal Instincts, Guinea Pig Whispering and Cuddling Tips
You need to be weighing them weekly so the tips in the guide will also help so you can get their weight checks done a bit more easily
How To Pick Up And Weigh Your Guinea Pigs Safely
Dexter was taking food from me and stopped running away from me after six weeks but Popcorn was still terrified. I could see over time that Pops become interested in me but he would run off and hide when I went to their shed, wouldnt come out, wouldnt take food from me. I continued with the piggy whispering tips, continued doing the same things and had to be very patient but all the time knowing that it may never happen with him - he may spend his whole life scared of me as he is of a more nervous character. A year and a half after they came to me, one morning I offered food to Popcorn by hand as I always tried but this time he took it from me. I couldn't believe it! Offered him another piece and he also took that. I think he had been watching Dexter do it for so long and nothing bad had happened to him that he realised he was safe! Suddenly a year and a half's work and patience had paid off. It's now been three years and still while neither of them like being held, they both come running to the front of the cage to see me when I enter their shed, they both take food from my hand, they both excitedly run around my feet as I get in with them. Also, if they are in the right mood, they will let me stroke them on the head or scratch under the chin - it doesnt happen a lot mind but they will allow it on occasion!