recently this is what i do to train. im currently aiming to improve the size of my chest and biseps.

20x3 6kg dumbell lift for both hands
20x4 wide arm push up
+ muscle juice supplement after training and before sleep at nite

doing this regime alternately between days. (1day do, 1 day rest, 1 day do..)

after 1 day, i could feel the pain my my muscles in the targeted area, so i rest for 1 day before training again. however, after doing it for a while. i dont feel pain anymore after i train. should i keep training until i feel the pain in the muscle again or i should just let the muscle rest? how do i know if my training is adequate?