You can't foam fill tires yourself, at least not normally. It is common to take your tires some place and have them do it.
The place I used required that the tires be left overnight to be sure they were cured properly before used.
My tractor dealer said that different places can make the foam filled tires harder or softer. Some softness is desirable. One person here has reported he broke front axle spindles with foam filled tires on the front of his tractor. I forget what tractor it was and whether it was 2 or 4 wheel drive. It is reasonable that some flex would be more desirable than concrete in the tires...less shock load on the front end components.
The place I used was recommended by my dealer as doing a good job and not making the tires too hard. They are still relatively hard though. I have over 500 hours on the front tires on my
B2910 Kubota without problem. I had those tires foam filled after getting my first flat at about hour two of tractor ownership. I am glad I did. It cost me about $70 per tire two years and 8 months ago.
I had the front tires of my
BX2200 foam filled last summer at a cost of $38 per tire.
The foam add a lot of weight. You will be surprised at the before and after weight. They charge by the pound for the foam fill around here I think.
I have no regrets and if I bought a third tractor, I would foam fill the front tires on it too. I am that happy with it.
When they foam fill the tire, they take out the valve core and drill a hole in the other side of the tire. When you get the tire back there is a sheet metal screw in that hole. The hole lets air out as the foam goes in...
Hope this helps.