The basics of the 4mil is that the piston goes 2 mm up into the head and down 2 mm below the transfers, so the head needs to be cut for proper squish clearance, squish band width, and volume and the bottom of the transfers need to be dropped 2mm. Once that's all squared away, then you get into degreeing in the port timings and transfer port angles. If you want to do your own porting, you need a right angle Foredom and you need to do LOTS of reading.
If you want to do your own porting, that's great, but you need to consider your motives.
"I saved money" "No you didn't. How much money could you have made in your machine shop in all the tons of hours you spent researching and porting?"
"I ported it myself" "Yeah, and I just smoked your ass with my ___________ professionally ported stock stroke"
"I don't understand why this thing needs 480 main jets" "Maybe your homebrew port job is whacked"