Choose photo you want to reference.
I Choose this Photo.
If you want to draw big, just print the face only and just make freehand in some different details.
You need to put some mark using pencil every end of the details and connect it (Vertical)
(Same as in step 2 but horizontal lines)
Up and Down in Lips, Eyes and mouth.
Cut every side of the paper in your reference just 1.5 inch so that you can copy the gridline into your Sketchpad, but if your sketchpad is bigger than the size of your reference its okay do not cut it.
How to copy the gridlines from your Reference into your drawing board?.
Put your sketchpad or drawing under your reference.
Put marks every end of your gridline reference and if you done copy all marks in gridlines connect it. (Vertical and Horizontal)
This is it ! But if you connect all marks dont make it hard to connect just a light marks and lines so that you can easily to erase it.
You can start now your sketch.
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If you are using android phone you can download this gridline app.
https://play.google.com/store/apps/details?id=com.nullpointer85.android.gridDrawing&hl=en&referrer=utm_source%3Dgoogle%26utm_medium%3Dorganic%26utm_term%3Dgrid+line+drawing&pcampaignid=APPU_1_EWDHV6TEOcmNgAaCjrvwCg