Well, it all depends ihn the gainer.
And what they like and can digest well.
In general it’s about the daily calorie intake. To get fat calorie denser foot is key, the combination of fat and carbs is perfect.
The easy Way is to start having shakes. With cream and weight gainer.
Other easy ways are just to have regulars, like ice cream every other night.
Drinking mainly soda
And just stuff as often as possible …
The problem with is that these are usually not the healthiest ways.
If you want to take care of health I would suggest counting calories and and adjust the daily intake.
With weekly weigh in.
Making sure u have a healthy diet with low unsaturated fats. Complex carbs a lot of fruits and veggies …
I mean you can compromise like having a good diet with regular stuffings.
10 months