yellow beans are good for starters... fill 80% allow for impact to compress bag or you can split zipper etc...
Hit bag a few times [10-15 punches] and check in between your knuckles for a small red 'tattoo' mark aka a blood blister, forming from heat/friction under the skin. Stop ! before it bleeds on bag [hygiene] and it takes 3 weeks before you can hit again...
when you make red mark on fist turn to open vertical palm strikes, you will develop blister at base of palm same way if not careful, so stop and cool down. Check often...
next day add a few more punches, and so on...try 500 between forms, run 5 miles have bag in backpack, use bungee cord to strap to available tree , hit , forms, hit, forms hit tree too
then run more..fitness just as important for punching...
You can make a narrow hanging bag out of an old jacket sleeve filled with small rocks/pebbles/shingle, wrap in gaffer tape for jum sao elbow in horizontal palm strikes .
For kicking fill wall bag [larger] with shingle/rocks etc....
No better object to hit and kick than the Thai long bag.
On another note, the fists pass next to each other, either side of the line not over and under, very important to repeat this early or you ingrain straightlines rather than sweeping , striking natural intercepting lines..iow lin sil di dar starts asa you do chain punch....forget fast punching , try good line sweeping strikes with body behind them.