We have been using the Wahl Cordless Colour Pro for about 2 years on our little boys.
They cost £34 on Superdrug and don’t have the best reviews on there (Possibly as they’re mislabelled as a beard trimmer) but have over £2k on Amazon and are selling for nearly £100 on there too!
It’s relatively straight forward to do, start with a grade 8 all over if you’re giving yourself a haircut (you can always go shorter!) The scissors can be helpful for trimming sideburns and around the hairline.
Plenty of tutorials on YouTube.