Hey Ishaa,
It's so good that you're willing to let your son explore his creative side rather than taking the pen off him
We started giving our son opportunities to draw with chalk and to paint when he was three months old. We let him hold his pens, crayons and paint brushes in whatever manner it felt comfortable but he was holding a pen correctly and with control by one simply through copying us.
We try not to "teach him" how to colour in etc as at this point it's more about the concept of making marks and developing fine motor skills as well as giving them a chance to become creative. Before he was two he was drawing pictures (some of which we could actually recognise before he told us what they were - many we still can't see what he sees
)
We were told by an occupational therapist for children that drawing on walls (not actually the walls but on a vertical surface) was recommended for beginners because it helped them to develop arm strength and control, put less pressure on the wrist and that the position encouraged finger holding rather than fist holding and this natural ease is one of the reason children love to draw on walls. The other is that they just can't help but see the wall as blank canvas
We blu tacked butchers paper to the walls in each room and made him understand through positive re-inforcement that he could draw on the paper but not the walls. Giving him a creative spot in each room meant once he caught on we didn't have to worry and he could draw any time the fancy took him.
Another great tool are soft pastels - the colours are so vibrant (even the white) and they make marks with very little pressure being applied which is very rewarding for young children (be warned it stains carpet and don't let wet chalk near your walls it takes forever to get off).
We often make things out of cardboard boxes (our sons trampoline boxes were huge so we made a big bus) and then we decorate these altogether. It's great fun for all of us, the pastels work really well on cardboard, and becomes an art project that can be continued - the bus lasted us three weeks before we pulled it apart and now the bottom half is used for his soft toys, all decorated by himself. We found that when he was younger cardboard was easier for him as he didn't poke holes in it. They find it hard to control the amount of pressure when they first start.
We were also told by the OT & a child psychologist that when we paint or colour in with him to stay only one step a head of him. So if he's using his whole arm to scribble you scribble too but using your wrist and fingers rather than drawing pictures or colouring in when they're not at that stage as it can turn them off. We kind of mixed it up a bit and did both because we wanted him to see what can be achieved with pen and paper but we also understood that we needed to break the learning process down into bite sized chunks for him.
There are some really good recipes (just google it - if you cant find any let me know and I'll dig mine out and post them for you) for bath tub paints which gives them a lot of fun and then they're already in the right place to be cleaned up!!!
Enjoy the process it's so much fun doing art like a toddler again, I enjoy everything I do with my son but I think art would be my favourite (probably because I'm not really much better than he is
)