Trouble getting Crank shaft bolt out

[xp190]

Hi guys

I'm in the process of changing a cracked timing rail, and I'm having a tough time getting the crank shaft bolt out. The 28mm one.

I don't have any air tools, but I do have tools I can use, my problem is I can't lean on this sucker hard enough without the engine spinning backward. The manual states that this should never take place.

I wanted to know if there is any trick I could use to freeze the engine from moving so I can get this bolt out and continue on with the job.

TIA

xp